feat(provisioning): game-account signup, admin email invites, unlink (2.0)

Phase 5: the account-provisioning backend — link-only stays, plus hybrid
self-signup, an admin email-invite tool, and site-side unlink.

- uoLinkClient.createAccount / unlinkAccount (v2). Password is forwarded to the
  shard (hashed there) and never stored/logged; the end-user browser IP is passed
  for the shard's per-IP cap; actor is stamped server-side.
- Hybrid signup: POST /player/shard/account provisions a game account (its own
  username + password) for the signed-in user and mirrors the link locally. Gated
  by the new game_account_signup setting AND the shard's own mode (mapped 403/409/
  429/400/503). Serves both self-serve signup and the invite-accept game step.
- Email invites: user_invites table (sha256 token hash, single-use, expiring);
  invites model + admin CRUD (POST/GET/DELETE /admin/invites, admin-only) +
  mailer.sendInvite (falls back to returning the accept link if email is off);
  public token-gated accept (GET /auth/invite/:token, POST .../accept) creates the
  user at the invite's preset role and logs them in, bypassing the registration
  gate. Accept is race-safe (atomic single-use; rolls back the user if it loses).
- Admin unlink: DELETE /admin/users/:id/shard/link/:account (admin-only) + local
  mirror drop; account.unlinked ingest reconciles the mirror when a player runs
  [unlink in game. account.audit / account.unlinked are logged (admin channel
  only — never on the public SSE allowlist).

Tests: invites model (hashing, single-use, expiry, revoke) + account.* ingest
reconcile/visibility. Full suite 193/193; swagger regenerated.

Refs .plans/protocol2-integration.md (Phase 5).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/router/v1/player/player.routes.js

@@ -148,6 +148,25 @@ playerRouter.post(
   validate,
   shard.link,
 )
+playerRouter.post(
+  '/shard/account',
+  // #swagger.tags = ['Player · Shard']
+  // #swagger.summary = 'Create a game account (hybrid signup) and link it to the caller'
+  // #swagger.description = 'Provisions a new game account with its own username + password and auto-links it to the signed-in website user. Available only when game_account_signup is enabled and the shard accepts website signups. The password is hashed on the shard and never stored or logged by the site.'
+  // #swagger.security = [{ "cookieAuth": [] }, { "bearerAuth": [] }]
+  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { type: "object", required: ["account","password"], properties: { account: { type: "string" }, password: { type: "string" } } } } } */
+  /* #swagger.responses[201] = { description: 'Account created and linked', content: { "application/json": { schema: { type: "object", properties: { account: { type: "string" }, linked: { type: "boolean" } } } } } } */
+  /* #swagger.responses[400] = { description: 'Validation error or rejected name/password', content: { "application/json": { schema: { $ref: "#/components/schemas/ValidationError" } } } } */
+  /* #swagger.responses[403] = { description: 'Game-account signup unavailable (site or shard)', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  /* #swagger.responses[409] = { description: 'Account name already taken', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  /* #swagger.responses[429] = { description: 'Per-IP account cap reached', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  /* #swagger.responses[503] = { description: 'Shard unavailable — retry', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  accountChangeLimiter,
+  body('account').matches(/^[A-Za-z0-9][A-Za-z0-9_.-]{2,29}$/),
+  body('password').isString().isLength({ min: 8, max: 64 }),
+  validate,
+  shard.createGameAccount,
+)
 playerRouter.get(
   '/shard/accounts',
   // #swagger.tags = ['Player · Shard']