refactor(api): collapse /admin/account and /player/account onto /auth/me/account

Self-service account security had three URL surfaces onto one controller. All
three mounted the same `admin/account.controller.js` handlers; each of the three
router files carried a header comment apologising for the arrangement.

`/auth/me/account` was already a strict superset, which settles which to keep:

  /admin/account   6 routes  noindex, isLoggedIn, staffOnly
  /player/account  8 routes  noindex, requireAuth
  /auth/me/account 10 routes noindex, requireAuth

Neither of the deleted surfaces carried recovery codes, and /admin/account
carried no username or password change at all — so client.js already called
/auth/me/account/recovery-codes/* for two operations on a screen it otherwise
served from /admin/account. The split was leaking before this change.

Gating is equivalent where it overlapped: /player and /auth/me apply identical
`noindex, requireAuth`, and `staffOnly` on /admin/account was strictly narrower
while buying nothing, since every handler is self-scoped to req.user.id. There
is no CSRF layer to differ.

  - 14 routes deleted, 0 added, no handler changed.
  - account.controller.js moves router/v1/admin/ -> router/v1/auth/, beside the
    one router that still reaches it.
  - Web client: 14 call sites move onto a root-level api.myAccount /
    api.changeUsername / ... group, matching the /auth/me methods already there.
  - Android app: no change. MeApi.kt was already 100% /auth/me/account/*.
  - Two swagger tags, `Admin · Account` and `Player`, were declared only by the
    deleted routes and go with them. The orphaned `AccountStatus` schema goes
    too; `PlayerAccount` is re-described as the any-role /auth/me/account shape
    (the name is kept so existing $refs resolve).

Breaking to the published OpenAPI surface, accepted deliberately: both consumers
are in this org, and deprecate-then-delete would leave the next phase deciding
whether to add routes to surfaces already marked for removal.

Verification: routes.manifest.json shows exactly 14 deletions and 0 additions.
The OpenAPI spec loses the same 14 paths with zero surviving path definitions
changed; its large textual diff is pure reordering, because removing the
first-mounted router shifts every later path. 1203 server tests, 288 client
tests, 53 bot tests green; check:modules, check:hosts and routes:manifest
--check all pass.

Design of record: docs/website/ENGAGEMENT.md Phase 1a. This lands ahead of
engagement Phase 1b, which adds a self-service email field — written once here
rather than three times.

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

server/src/router/v1/admin/index.js

@@ -16,7 +16,6 @@ const express = require('express')
 const { isLoggedIn, requireRole } = require('../../../utils/auth')
 const noindex = require('../../../middleware/noindex')
 
-const accountRouter = require('./account.router')
 const usersRouter = require('./users.router')
 const invitesRouter = require('./invites.router')
 const authProvidersRouter = require('./authProviders.router')
@@ -48,7 +47,6 @@ const adminRouter = express.Router()
 const staffOnly = requireRole('admin', 'editor', 'moderator')
 adminRouter.use(noindex, isLoggedIn, staffOnly)
 
-adminRouter.use('/account', accountRouter)
 adminRouter.use('/users', usersRouter)
 adminRouter.use('/invites', invitesRouter)
 // Mounted at /auth, not /auth/providers: /admin/auth is the capability, and the