feat(frontend): make Storybook a validated, fully covered component workbench

Storybook existed only as an undocumented local tool: 9 of 24 reusable components had stories, autodocs pages were bare prop tables, nothing built or tested the stories, and no contributor doc mentioned the workbench existed.

Every reusable component under src/components/ now has a co-located story with enriched autodocs (component descriptions plus per-prop argTypes, kept as string metadata since the repo bans line comments). Stories double as headless Chromium tests through the Storybook vitest addon, with axe accessibility checks enforced as errors and play-function interaction tests covering the modals, the RHF field bridge, the config block, and the select-all buttons. The preview now mirrors the panel's real theme DOM (body class, shared AntD theme config, seeded theme storage) so what stories render matches production.

CI and make verify gain a static Storybook build as a compile gate, and the frontend test job installs Chromium so story tests run on every PR. Contributor docs (frontend README, CONTRIBUTING, agent guides) document the workbench, the story conventions, and the Controls setup. Node engines move to 24 LTS and gen:api drops the type-stripping flags that Node 24 makes default.

CONTRIBUTING.md

@@ -5,7 +5,7 @@ Thanks for taking the time to contribute to 3x-ui. This guide gets a development
 ## Prerequisites
 
 - **Go 1.26+** (the version pinned in `go.mod`)
-- **Node.js 22+** and npm 10+ (for the React frontend)
+- **Node.js 24 LTS** (the version pinned in `.nvmrc`) and npm 10+ (for the React frontend)
 - **Git**
 - **A C compiler** — required by the CGo SQLite driver (`github.com/mattn/go-sqlite3`). Linux and macOS already ship one; for Windows see below.
 
@@ -157,12 +157,13 @@ Panel navigation happens client-side through React Router, and per-route code is
 
 Locale strings live in `internal/web/translation/<locale>.json`, **not** under `frontend/`. The Go binary embeds the same JSON and serves it to both backend templates and `react-i18next` (initialized in `src/i18n/react.ts`). When a new English key is added it must also land in **every** non-English locale — missing keys do not break the build, they just render the raw key in the UI.
 
-### Two dev workflows
+### Dev workflows
 
 | Goal | Command |
 |------|---------|
 | Iterate on UI changes with HMR | `cd frontend && npm run dev` (Vite on `:5173`, proxies `/panel/*` and the WebSocket to the Go panel on `:2053`). Start the Go panel first. |
 | Verify what end users actually see | `cd frontend && npm run build`, then `go run .`. The Go binary serves the built bundle — embedded in release mode, off disk in debug mode. |
+| Develop/preview a reusable component in isolation | `cd frontend && npm run storybook` (Storybook workbench + autodocs on `:6006`). |
 
 The Vite dev proxy serves the admin SPA for any `/panel/*` URL — `bypassMigratedRoute` in `vite.config.js` rewrites those requests to `index.html` and lets React Router take over — while forwarding `/panel/api/*`, `/panel/api/setting/*`, `/panel/api/xray/*`, and the WebSocket to the Go panel. Because routing is now client-side, new panel routes need no proxy or allowlist changes.
 
@@ -189,6 +190,7 @@ Only a genuinely **standalone bundle** (like `login` or `subpage`, reachable wit
 - **Document new endpoints.** Every new `g.POST`/`g.GET` in `internal/web/controller/` needs a matching entry in `src/pages/api-docs/endpoints.ts` — it drives both the in-panel API docs and the generated OpenAPI/Zod (`npm run gen:api` / `gen:zod`).
 - **Do not break link generation.** Share-link logic lives in `src/lib/xray/` (`inbound-link.ts`, `outbound-link-parser.ts`, …) and is round-tripped by the golden fixture suite — run `npm run test` after any change to URL generation, defaults, or TLS/Reality handling, and regenerate snapshots (`npx vitest run -u`) only for intentional changes. Two runtime paths consume it: the **inbounds page** and the **clients page** subscription links (`/panel/api/clients/subLinks/:subId` → backend `GetSubs`); exercise both.
 - **Vite is pinned to an exact version** (no `^`) in `frontend/package.json` — read the live version there rather than trusting a number quoted here — so local, CI, and release builds resolve identically. Bump it deliberately and verify both `npm run dev` and `npm run build` afterward.
+- **Reusable components are documented in Storybook.** When you add or change a component in `frontend/src/components/`, add or update its co-located `<Component>.stories.tsx` (`tags: ['autodocs']`), documenting props via `argTypes` / `parameters.docs` string metadata rather than JSDoc. CI compile-checks every story via `npm run build-storybook` and runs each story as a headless-browser test via `@storybook/addon-vitest` (`npm run test`, needs `npx playwright install chromium`); run `npm run storybook` to preview locally.
 
 ### Project layout
 
@@ -277,7 +279,7 @@ CI runs this for you nightly (and on demand) via `.github/workflows/mutation.yml
 
 ### CI
 
-`.github/workflows/ci.yml` runs per PR: `go-test` (with `-shuffle -count=1`), a `race` job (`-race -shuffle -count=1`), a `fuzz-smoke` job on the critical parsers, and the frontend `typecheck`/`lint`/`test`/`build`. Snapshots are regression guards — regenerate them (`npx vitest run -u`) only for intentional output changes, never to make a red test green.
+`.github/workflows/ci.yml` runs per PR: `go-test` (with `-shuffle -count=1`), a `race` job (`-race -shuffle -count=1`), a `fuzz-smoke` job on the critical parsers, and the frontend `typecheck`/`lint`/`test`/`build`/`build-storybook`. Snapshots are regression guards — regenerate them (`npx vitest run -u`) only for intentional output changes, never to make a red test green.
 
 ## Sending a pull request
 
@@ -286,7 +288,7 @@ CI runs this for you nightly (and on demand) via `.github/workflows/mutation.yml
 3. Run the relevant checks before pushing:
    - `go build ./...`
    - `go test ./...` (when Go code changed)
-   - `cd frontend && npm run typecheck && npm run lint && npm run test && npm run build` (when the frontend changed; CI runs this same set on every PR via `.github/workflows/ci.yml`)
+   - `cd frontend && npm run typecheck && npm run lint && npm run test && npm run build && npm run build-storybook` (when the frontend changed; CI runs this same set on every PR via `.github/workflows/ci.yml`)
 4. Commit messages follow the existing pattern in `git log` — `<area>: short imperative summary`, then a body explaining the *why*. Conventional-commit prefixes (`feat`, `fix`, `refactor`, `chore`, `style`, `docs`) are encouraged.
 5. Open the PR against `main` with a brief description of what changed and how to test it.