chore(server): freeze the URL surface with a generated route manifest

PR 0 of the router domain split (docs/website/API_V2_PLAN.md § Phase 2). The
split promises that admin.routes.js can be carved into one router file per
business capability without moving a single URL. That promise has to be proved
by a diff, not asserted in review — this lands the tool that proves it, with no
router file moved.

scripts/routeManifest.js walks the live Express stack (runtime introspection,
not source parsing: route paths in admin.routes.js sit on the line *after*
`adminRouter.get(`, which defeats greps) and writes a sorted { method, path }
list to routes.manifest.json. It reproduces the frozen baseline in
docs/website/api-route-inventory.json byte-for-byte — 199 public routes plus 2
on the internal listener — so the freeze is confirmed accurate, not just
claimed.

Scope is /api/** and /.well-known/** plus the internal app. The SPA catch-all,
/uploads and /brand are filesystem-conditional static mounts, so including them
would make the output depend on whether CI had built the client. Static mounts
are not API contract.

Also emits routes.guards.json — a review aid, not a contract: per route, the
handler count and the *named* middleware on its mount chain. Router-level
`use(noindex, isLoggedIn, staffOnly)` gates never appear in an individual
route's own stack, so an extracted capability router that forgot to re-apply
one would otherwise publish authenticated endpoints silently. Names are a hint
only (requireRole(...) returns an anonymous arrow), but a vanished requireAuth
is unambiguous — and the test suite asserts every /admin/** and /player/**
route still carries it.

The plan's optional unauthenticated-status snapshot was tried and dropped, as
it allowed: against the dead-port mariadb pool the tests use, the sweep sits on
the pool's acquire timeout and had not finished after two minutes. A flaky
two-minute gate is worse than none; the requireAuth assertion covers the same
regression deterministically.

CI runs `npm run routes:manifest -- --check` on every PR, so a URL change can
only merge by deliberately committing the new manifest.

Co-Authored-By: Claude <noreply@anthropic.com>

CONTRIBUTING.md

@@ -54,6 +54,12 @@ If you add or change an API route, regenerate the Swagger spec
 (`cd server && npm run swagger`) and commit the updated
 `server/swagger/swagger-output.json`.
 
+The URL surface is also frozen by a generated manifest. If your change adds,
+removes or renames a route, regenerate it (`cd server && npm run routes:manifest`)
+and commit `server/routes.manifest.json` + `server/routes.guards.json` — CI fails
+otherwise. A non-empty diff in `routes.manifest.json` means you changed the API
+contract, so call it out in the PR description; a pure refactor must produce none.
+
 ## Branch & PR workflow
 
 1. Fork or branch from `main`. Use a descriptive branch name