feat(sub): client-side balancers for the JSON subscription (#6243)

* feat(sub): add SubBalancer model and migration

Client-side JSON-subscription balancer row: remark, strategy, member inbound ids, sort order, enabled. Registered in allModels and migrationModels so AutoMigrate and SQLite->Postgres copy pick it up.

* feat(sub): add SubBalancer service

List/Get/Create/Update/Delete over the sub_balancers table with remark trim, strategy allowlist (leastLoad/leastPing/random) and sort-order floor. Rows are read per request by the subscription builder, so mutations need no xray restart.

* feat(sub): add SubBalancer API controller and routes

GET/POST /panel/api/sub-balancers, POST /:id (update), DELETE /:id and POST /:id/del alias. inboundIds bind from repeated form keys. Mounted under the /panel/api group so the existing API token + CSRF middleware cover it.

* feat(sub): emit client-side balancers in JSON subscription

For each enabled balancer, append one config document whose outbounds are the selected inbounds' proxy outbounds retagged under a per-balancer prefix, with routing.balancers + burstObservatory selecting it. Balancer entries interleave with inbound entries by sort order; on equal numbers the balancer follows the inbound. Skipped when disabled or no member outbound is present.

* test(sub): cover SubBalancer service and JSON output

Service: validation gates (remark/strategy/inbound ids/sort order) and CRUD round-trip. JSON: balancer document shape, sort interleaving with inbounds, disabled/empty skip, and member tag dedup.

* feat(sub): add sub-balancers i18n keys

pages.settings.subBalancers.* block (menu, title, add, desc, field labels, strategy names, sort-order help, validation messages) added to all 13 locales.

* feat(sub): add SubBalancer schema and API queries

Zod schema (entity + form, strategy enum, validation messages wired to i18n keys), react-query hooks for list/create/update/delete, and the sub-balancers query key.

* feat(sub): add subscription balancers settings tab

SubscriptionBalancersTab lists balancers (sort order, remark, strategy, inbound count, enabled toggle, edit/delete) with a form modal (remark, strategy, sort order, multi-select inbounds filtered to multi-client protocols, enabled). Wired into SettingsPage under #subscription-balancers, and the sidebar shows the entry only when JSON subscription is enabled.

* test(sub): add SubBalancer form modal test

Covers add-mode (no validation errors, confirm with parsed values) and edit-mode (seeds from the balancer, preserves strategy/sort order/enabled).

* feat(sub): register sub-balancers in API docs and OpenAPI

Adds the sub-balancers endpoint group to endpoints.ts (list/create/update/delete + POST del alias) and regenerates frontend/public/openapi.json from it.

* docs: sync openapi.json with frontend

docs/public/openapi.json had fallen behind frontend/public/openapi.json (fewer paths/schemas). Copy the current frontend spec so the docs site renders the full API.

* docs: add subscription balancers API reference

Registers the sub-balancers page (generated MDX) and adds the sub-balancers paths to docs/public/openapi.json so the page renders the list/create/update/delete operations.

* feat(sub): accept roundRobin balancer strategy

Add roundRobin to the model oneof tag and the service strategy allowlist, alongside leastLoad/leastPing/random. Covered by a service-level create test that fails on the old allowlist.

* feat(sub): add roundRobin strategy label

pages.settings.subBalancers.strategyRoundRobin added to all 13 locales.

* feat(sub): expose roundRobin in balancer form

Zod strategy enum, form modal label key, and table strategy colour for roundRobin.

* docs(sub): list roundRobin in strategy description

The create/update strategy param description now mentions roundRobin alongside the other three.

* feat(sub): add subJsonObservatory setting

Panel-wide JSON string carrying the burstObservatory ping config (destination, connectivity, interval, sampling, timeout, httpMethod) emitted into client-side balancer docs. Stored like subJsonMux/Rules/FinalMask.

* feat(sub): wire observatory config through sub controller

WithSUBJsonObservatory option; the controller calls SubJsonService.SetObservatoryConfig after construction.

* feat(sub): emit observatory conditionally with configurable probes

burstObservatory is emitted only for leastPing/leastLoad; random/roundRobin get none (no fallback, so an observatory would only probe for nothing). Probe params come from the subJsonObservatory setting, falling back to the built-in defaults when empty or partial. Test covers the conditional emit and the override.

* feat(sub): add subJsonObservatory to AllSetting model

Frontend AllSetting model and Zod schema carry the new panel-wide observatory config string.

* feat(sub): add balancer observatory config card

New Sub Formats tab editing destination/connectivity/interval/sampling/timeout/httpMethod, stored as JSON in subJsonObservatory. Toggle off clears the setting; the backend then falls back to defaults.

* fix(sub): hide save/restart header on sub-balancers tab

Sub-balancer mutations are incremental (own CRUD API, no Save, no restart), so the page-wide 'every change needs to be saved / restart the panel' banner is misleading there. The in-tab alert already explains it correctly.

* feat(sub): add observatory config i18n keys

pages.settings.subBalancers.observatory.* (title, desc, probe field labels and help texts) added to all 13 locales.

* feat(sub): regenerate openapi for subJsonObservatory

openapigen picks up the new AllSetting field; openapi.json synced into docs.

* feat(sub): add observatory tab to sub-balancers

Mirrors the Xray Balancers page: two tabs (Balancers + Observatory).
Wires allSetting/updateSetting into the tab and adds tabBalancers /
tabObservatory labels to all locales. The page Save header is shown
again on this tab so the observatory config can be saved.

* refactor(sub): drop observatory tab from sub-formats

Now that the observatory config lives under sub-balancers, remove the
duplicate tab plus its state and defaults from sub-formats.

* fix(sub): add missing inboundsCount i18n key

The sub-balancers table rendered the raw key path in the Inbounds
column because pages.settings.subBalancers.inboundsCount was not
defined. Added it to all 13 locales.

* test(sub): pin disabled-inbound exclusion from balancer

The balancer builds its members from the subscriber's already-filtered
entry set, so an inbound disabled for that user can never surface as a
member. Adds tests for both shapes (one of several disabled, and the
only selected one disabled).

* fix(sub): make observatory toggle honest, default connectivity off, add balancer fallback

Three coupled defects on the balancer observatory surface, flagged in PR review:

- The Observatory Switch wrote '' which the Go side treats as "use built-in defaults", so leastPing/leastLoad still shipped a burstObservatory the admin could no longer see or edit. The observatory is mandatory for these strategies (Xray refuses to start leastPing/leastLoad without one — verified against Xray 26.7), so the switch is relabelled to "customise probe parameters vs built-in defaults" rather than on/off: '' keeps the defaults, a stored JSON overrides them. An info Alert explains this.

- Connectivity defaulted to http://www.google.com/generate_204 and an explicit {"connectivity":""} restored it, so the UI's "Leave empty to skip" was unreachable and the direct pre-check was dead on arrival on censored client networks. Default to "" and honour an explicit empty value.

- routing.balancers had no fallbackTag, so a leastPing/leastLoad balancer whose probes all fail selects nothing and dispatch fails. Emit fallbackTag pointing at the first member so a probe outage degrades instead of breaking.

Also skip balancer entries (kind!=0) in the member scan so a balancer can never match another balancer's row id. Tests cover each fix and fail without it.

* fix(sub-balancer): localize controller toasts and reject malformed ids

Route the new controller's user-facing messages through I18nWeb so non-English admins get localized toasts like every other controller, and switch parseID to strconv.Atoi rejecting ids < 1 so "12abc" and negative ids no longer coerce to a silent no-op delete that reports success.

* fix(sub-balancer): enforce remark length cap server-side

The model's validate:"max=256" tag was never enforced (parseSubBalancerForm binds an ad-hoc struct without validate.Struct), so a scripted API client could store an unbounded remark that is emitted verbatim as the remarks field of every affected subscriber's config. Reject len > 256 in validate() to match the frontend Zod cap.

* fix(sub-balancer): exclude mtproto from balancer member picker

SubJsonService.getConfig has no mtproto case, so an mtproto inbound's first outbound is "direct" and the buildBalancerConfig "tag != proxy" guard drops it — an admin could select it, save without error, and get a balancer that silently omits it (or no document at all). Drop it from the picker and fix the comment.

* docs(sub-balancers): add nav entry, fix tab pointer, note mirror scope

- Add "subscription-balancers" to the en reference/api meta.json pages array so the new MDX page is reachable from the sidebar (fa/ru/zh have no MDX — gen-openapi.ts emits into en only).

- Fix the endpoints.ts section description from "Settings -> Subscription" to "Settings -> Sub Balancers" (the feature's own tab) and regenerate the OpenAPI spec + MDX.

- Note in docs/lib/xray/subscription.ts that balancer documents are intentionally out of scope for that mirror.

* style(model): trim SubBalancer comment to 2-line cap

CLAUDE.md caps committed Go comment blocks at 2 lines; this one was 3.

* fix(sub-balancer): parse enabled explicitly and preserve it on partial update

parseSubBalancerForm treated any non-"false" value as true (so "bogus"
silently enabled) and always overwrote Enabled on update, so a PATCH that
omitted the toggle reset a disabled balancer back to enabled. Parse the
field with strconv.ParseBool and return *bool: absent means "no change"
on update and "true" on create; a malformed value is rejected as 400.
Update keeps the stored Enabled when the pointer is nil.

* fix(sub-balancer): clear deleted inbound from sub_balancers.InboundIds

DelInbound cascaded hosts but left the deleted inbound id in every
sub_balancers.InboundIds, so the balancer kept emitting a member no
subscriber could resolve — a dangling outbound tag with no proxy behind it.
Strip the id inside the existing delete transaction (same shape as the hosts
cascade, #5648); with the last member gone the balancer stops emitting.

* fix(sub-balancer): return not-found when deleting a missing balancer

Delete returned the gorm result error only, which is nil when no row matched,
so the controller reported success:true for an id that never existed — a stale
UI row looked like a clean delete. Check RowsAffected and return a not-found
error on 0 so the toast reflects reality.

* style(sub): shorten leastPing/leastLoad observatory comments

The observatory-emission guard comment and its test comment ran a few
lines long; trim them to a couple of lines each without dropping the
invariant that leastPing/leastLoad require a burst observatory.

* fix(sub): validate observatory setting instead of silently dropping it

SetObservatoryConfig applied whatever survived json.Unmarshal with no checks,
so a bad probe URL ("not-a-url"), non-duration interval/timeout, or even
unparseable JSON was either silently applied or silently ignored. Validate
each field: parse durations with time.ParseDuration, require http(s) URLs for
destination/connectivity, and log a warning naming the field and the bad value
on every fallback — including the unmarshal error, which was a quiet return.
Bad values now keep the built-in defaults instead of leaking into the emitted
burstObservatory.

* fix(sub): deduplicate burst-observatory defaults across Go and frontend

The burst-observatory ping defaults lived in three places that had drifted:
Go defaultSubBalancerObservatoryConfig (http probe, sampling 3), the Zod
PingConfigSchema, and DEFAULT_BURST_OBSERVATORY (both with a connectivity
pre-check URL). Align them to one set: https probe destination, sampling 2,
and empty connectivity (skip the direct pre-check). The settings tab now
parses the stored JSON through PingConfigSchema and seeds its default from
DEFAULT_BURST_OBSERVATORY instead of carrying its own literal.

* refactor(sub): extract proxy outbounds once before the balancer loop

buildBalancerConfig unmarshalled every inbound document and re-extracted its
first outbound on each balancer, so with B balancers and N inbound docs the
same document was parsed B*N times. Pull each doc's proxy outbound in a single
pre-pass over the entries and cache it per entry; buildBalancerConfig now
clones the cached map before retagging, so one parse serves every balancer.
Output is byte-for-byte unchanged.

* fix(sub): form balancer member tags from the inbound protocol, not tcp→vless

balancerTransport derived the bal-N tag suffix from the outbound's transport
network and hard-coded tcp→vless, so a vmess/tcp or trojan/tcp member was
mislabelled "vless" in every client config — the tag lied about the proxy
type. Use the outbound's real protocol as the suffix (bal-1-vmess, bal-1-vless,
bal-1-trojan, …) so the tag names the actual proxy; the selector prefix and
dedup suffix are unchanged. Update the existing tag assertions and add a vmess
case that fails under the old mapping.

* fix(sub-balancer): default strategy to random in the create form

The create-balancer form seeded strategy to 'leastLoad', but the service
validate() defaults an empty strategy to 'random' and the API docs say the
default is 'random' — so a freshly opened form showed leastLoad while saving
without touching the field silently stored random. Align the form default to
'random' so what the admin sees is what gets persisted.

* feat(api-docs): document the SubBalancer response schema

The five sub-balancer endpoints carried no responseSchema, so the API docs
page rendered them without a typed example. Add example: tags to every
SubBalancer field, allow the struct through openapigen, and point the list
(responseSchemaArray) and single-row endpoints at 'SubBalancer'. Regenerate
the Zod/JSON schemas and OpenAPI doc and mirror openapi.json into docs/.

* style(sub-balancer): drop whitespace-only separator lines, add final newline

subBalancer.ts and SubBalancerFormModal.tsx used single-space blank lines as
separators between statements and had no trailing newline. Replace them with
clean empty blank lines and end each file with a newline.

* fix(i18n): translate sub-balancer toasts and observatory note

The sub-balancer toast messages (list/create/update/delete/invalidId) and
the observatory note were left in English across 11 non-English locales
(ar, es, fa, id, ja, pt-BR, tr, uk, vi, zh-CN, zh-TW) while every other key
in the subBalancers block was already translated. Translate them to match the
meaning and terminology of the surrounding keys in each file; the JSON
structure and keys are unchanged.

* fix(sub-balancer): hide disabled inbounds from the member picker

The picker offered every protocol-eligible inbound regardless of its enable
flag, but getInboundsBySubId filters `AND inbounds.enable = true`. A disabled
member is therefore dropped from every subscriber's entries, and when it was
the balancer's only member the balancer document silently stops being emitted
— with nothing in the UI explaining why. TestSubJson_BalancerSkippedWhenAll
MembersDisabled already documents that backend behavior.

Filter the way the sibling client picker has since #5645: hide disabled
inbounds, but keep one that is already selected so editing an existing
balancer cannot silently drop a member.

Drop the `?? []` on the useWatch result so the new useMemo dependency stays
referentially stable.

* style(sub): trim the balancerMemberSuffix comment to the 2-line cap

Comment blocks in committed Go are capped at 2 lines; the name already carries
what the function picks, so keep only the why.

---------

Co-authored-by: Sanaei <ho3ein.sanaei@gmail.com>
Co-authored-by: claude[bot] <41898282+claude[bot]@users.noreply.github.com>

internal/web/translation/vi-VN.json

@@ -1386,7 +1386,56 @@
       "calendarGregorian": "Gregorian (Standard)",
       "calendarJalalian": "Jalalian (شمسی)",
       "ipLimitAllowlist": "Danh sách cho phép của giới hạn IP",
-      "ipLimitAllowlistDesc": "Các địa chỉ và mạng mà giới hạn IP không bao giờ tính và không bao giờ chặn, để một địa chỉ dùng chung của văn phòng hoặc trường học không dùng hết giới hạn của người dùng. IPs/CIDRs cách nhau bằng dấu phẩy."
+      "ipLimitAllowlistDesc": "Các địa chỉ và mạng mà giới hạn IP không bao giờ tính và không bao giờ chặn, để một địa chỉ dùng chung của văn phòng hoặc trường học không dùng hết giới hạn của người dùng. IPs/CIDRs cách nhau bằng dấu phẩy.",
+      "subBalancers": {
+        "menu": "Bộ cân bằng đăng ký",
+        "title": "Bộ cân bằng đăng ký",
+        "add": "Thêm bộ cân bằng",
+        "desc": "Mỗi bộ cân bằng đang bật được thêm vào đăng ký JSON như một hồ sơ riêng, tự động chọn điểm cuối tốt nhất trong các inbound đã chọn.",
+        "remark": "Ghi chú",
+        "remarkPlaceholder": "Tự động · nhanh nhất",
+        "strategy": "Chiến lược",
+        "strategyLeastLoad": "Tải thấp nhất",
+        "strategyLeastPing": "Ping thấp nhất",
+        "strategyRandom": "Ngẫu nhiên",
+        "strategyRoundRobin": "Luân phiên",
+        "sortOrder": "Thứ tự",
+        "sortOrderHelp": "Vị trí trong danh sách đăng ký, xen kẽ với thứ tự inbound; khi cùng số, bộ cân bằng đứng sau inbound.",
+        "inbounds": "Inbound",
+        "inboundsCount": "{count} Inbound",
+        "enabled": "Đã bật",
+        "empty": "Chưa có bộ cân bằng nào",
+        "deleteConfirm": "Xóa bộ cân bằng này?",
+        "errRemarkRequired": "Cần nhập ghi chú",
+        "errInboundsRequired": "Chọn ít nhất một inbound",
+        "errSortOrder": "Thứ tự phải là số nguyên ≥ 1",
+        "toasts": {
+          "list": "Không thể liệt kê các bộ cân bằng đăng ký",
+          "create": "Không thể tạo bộ cân bằng đăng ký",
+          "update": "Không thể cập nhật bộ cân bằng đăng ký",
+          "delete": "Không thể xóa bộ cân bằng đăng ký",
+          "invalidId": "Id không hợp lệ"
+        },
+        "tabBalancers": "Cân bằng",
+        "tabObservatory": "Observatory",
+        "observatory": {
+          "title": "Đài quan sát bộ cân bằng",
+          "desc": "Tham số probe cho burstObservatory nhúng vào mỗi hồ sơ leastPing/leastLoad. random/roundRobin không có đài quan sát. Lưu thành cài đặt chung của đăng ký JSON.",
+          "destination": "URL probe",
+          "destinationDesc": "Địa chỉ client thăm dò để đo mỗi outbound thành viên.",
+          "connectivity": "URL kết nối",
+          "connectivityDesc": "Địa chỉ tuỳ chọn để kiểm tra một lần thành viên có tới đích được không. Để trống để bỏ qua.",
+          "interval": "Khoảng probe",
+          "intervalDesc": "Thời gian giữa các vòng probe, vd. 1m.",
+          "timeout": "Hết giờ probe",
+          "timeoutDesc": "Hết giờ cho mỗi probe, vd. 5s.",
+          "sampling": "Lấy mẫu",
+          "samplingDesc": "Số lần probe liên tiếp để trung bình độ ổn định.",
+          "httpMethod": "Phương thức HTTP",
+          "httpMethodDesc": "Phương thức dùng cho yêu cầu probe.",
+          "note": "Các bộ cân bằng leastPing/leastLoad luôn mang một burstObservatory. Công tắc này tùy chỉnh các tham số probe — tắt nó để dùng mặc định tích hợp. Các thay đổi áp dụng sau khi khởi động lại bảng điều khiển."
+        }
+      }
     },
     "xray": {
       "importRules": "Nhập quy tắc",