feat(sub): leastLoad member weights for subscription balancers (#6304)

* feat(model): add MemberWeights to SubBalancer

Per-inbound leastLoad weights, stored with the same gorm json serializer
as InboundIds so AutoMigrate adds the text column on every dialect
(postgresModelSettled sees the missing column and re-runs). Absent
entries mean weight 1.0; only meaningful for strategy leastLoad.

* feat(sub): accept memberWeights on the sub-balancer API

Parsed as one JSON form field (gin cannot bind bracket-keyed maps from
urlencoded bodies). validate() rejects weights under any strategy but
leastLoad — xray would silently ignore costs there, so storing them
would pretend a knob exists. Non-positive weights error instead of
defaulting: a zero usually means a typo'd "never pick this node".
Entries for inbounds no longer selected are dropped on save.

* feat(sub): emit leastLoad strategy costs from member weights

costs[] is built after the tagging loop reuses the exact retagged tags
(bal-N-protocol[-k]) and each member's owning inbound id. Members
without a configured weight default to 1.0, but costs are omitted
entirely unless at least one explicit weight survives — an all-1.0
array would bloat every subscription response for no effect.

* feat(sub-balancers): leastLoad member weight inputs

Weight fields render only under leastLoad and hide on strategy change
without dropping their values, so an accidental toggle away and back
loses nothing until save; non-leastLoad submits strip them entirely
because xray would ignore costs. Weights travel as one JSON form field
(gin cannot bind bracket-keyed maps) and every locale gets the three
new keys in the same commit per the dead-keys rule.

* docs(api): document memberWeights on sub-balancers

leastLoad-only JSON form field; update notes that omitting it clears
stored weights. Regenerated openapi artifacts via make gen + the docs
copy/gen:api step nothing checks automatically.

* fix(api-docs): use the allowed object ParamType for memberWeights

* fix(sub-balancers): cap the member-weight list height

Many selected inbounds pushed the modal body past the viewport. The
weight rows now scroll inside a 220px viewport, mirroring the inbound
picker's listHeight so both lists read the same.

* fix(sub): anchor leastLoad cost matches to exact member tags

Verified against xray-core: without regexp, WeightManager matches costs
by substring (strings.Index), so the bare tag "bal-1-vless" also hits
the deduplicated "bal-1-vless-2" and both members get the first
entry's weight. Anchored ^tag$ regexps make every cost entry match only
its own member. Also confirmed value<=0 makes xray derive a weight from
the first digit of the matched tag — validating weights > 0 server-side
was the right call.

* fix(sub-balancers): keep member weights across the enabled toggle

The table's toggleEnabled re-posted a full-row payload without
memberWeights, and the update path treats an absent key as "erase" —
flipping the switch silently dropped every configured weight. Round-trip
the stored weights through the toggle payload, and prove persistence
with a re-Get in the weight-validation test (the returned struct alone
would stay green even if Save skipped the column).

* fix(sub-balancers): address review on member weights

- omitempty on MemberWeights: the panel sends null for every pre-existing
  and non-leastLoad balancer, which failed the hand-written zod response
  schema on every fetch (zod .optional() accepts undefined only; switched
  to .nullish() per repo convention) and drifted the generated contract.
  Regenerated openapi artifacts + docs copy + MDX.
- Bound weights to the positive float32 range: xray decodes costs as
  float32, so an over-range value makes clients reject the whole
  subscription document and an underflow decays to the tag-digit
  fallback weight. Tests for both directions.
- Trim six comment blocks to the 2-line cap from CLAUDE.md.

---------

Co-authored-by: DIMFLIX <dimflix@users.noreply.github.com>

internal/sub/json_service.go

@@ -351,12 +351,49 @@ func balancerMemberSuffix(protocol string) string {
 	return protocol
 }
 
+// balMember is one retagged member outbound and the inbound it came from.
+type balMember struct {
+	tag       string
+	inboundId int
+}
+
+// leastLoadCosts builds xray's static strategy costs: higher value = picked
+// less often; nil unless a member carries an explicit weight (all-1.0 bloat).
+func leastLoadCosts(balancer *model.SubBalancer, members []balMember) []any {
+	if balancer.Strategy != "leastLoad" || len(members) == 0 || len(balancer.MemberWeights) == 0 {
+		return nil
+	}
+	costs := make([]any, 0, len(members))
+	configured := false
+	for _, m := range members {
+		value := 1.0
+		if weight, ok := balancer.MemberWeights[m.inboundId]; ok && weight > 0 {
+			value = weight
+			configured = true
+		}
+		// Anchored regexp: plain cost matching is substring-based in xray, so
+		// an unanchored "bal-1-vless" would also swallow "bal-1-vless-2".
+		costs = append(costs, map[string]any{
+			"regexp": true,
+			"match":  "^" + m.tag + "$",
+			"value":  value,
+		})
+	}
+	if !configured {
+		return nil
+	}
+	return costs
+}
+
 // buildBalancerConfig assembles the balancer profile: members retagged under a
 // per-balancer prefix, a routing.balancers entry, and (for leastPing/leastLoad) an observatory.
 func (s *SubJsonService) buildBalancerConfig(balancer *model.SubBalancer, entries []subConfigEntry, entryProxies [][]map[string]any) json_util.RawMessage {
 	prefix := fmt.Sprintf("bal-%d-", balancer.Id)
 	usedTags := make(map[string]bool)
 	var proxies []json_util.RawMessage
+	// Members in emission order with their owning inbound, so costs[] can
+	// reference the exact retagged tags assigned here.
+	var members []balMember
 	var firstTag string
 	// entryProxies is the pre-extracted proxy outbounds per entry; kind!=0 rows
 	// have none. Clone before retagging so the cached map stays reusable.
@@ -375,6 +412,7 @@ func (s *SubJsonService) buildBalancerConfig(balancer *model.SubBalancer, entrie
 			member := maps.Clone(outbound)
 			member["tag"] = tag
 			if raw, err := json.MarshalIndent(member, "", "  "); err == nil {
+				members = append(members, balMember{tag: tag, inboundId: entry.id})
 				if firstTag == "" {
 					firstTag = tag
 				}
@@ -411,10 +449,14 @@ func (s *SubJsonService) buildBalancerConfig(balancer *model.SubBalancer, entrie
 	}
 	routing["rules"] = rules
 	isObservatory := balancer.Strategy == "leastPing" || balancer.Strategy == "leastLoad"
+	strategyEntry := map[string]any{"type": balancer.Strategy}
+	if costs := leastLoadCosts(balancer, members); costs != nil {
+		strategyEntry["settings"] = map[string]any{"costs": costs}
+	}
 	balancerEntry := map[string]any{
 		"tag":      subBalancerTag,
 		"selector": []string{prefix},
-		"strategy": map[string]any{"type": balancer.Strategy},
+		"strategy": strategyEntry,
 	}
 	if isObservatory && firstTag != "" {
 		// With all probes failing, route to the first member instead of