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/auth/auth.routes.js

@@ -1,7 +1,8 @@
 const express = require('express')
-const { body } = require('express-validator')
+const { body, param } = require('express-validator')
 
 const { login, register, loginTotp, logout, me, HONEYPOT_FIELD } = require('./auth.controller')
+const { getInvite, acceptInvite } = require('./invite.controller')
 const { isLoggedIn } = require('../../../utils/auth')
 const { attachSession } = require('../../../auth/session.middleware')
 const { loginLimiter, registerLimiter } = require('../../../middleware/rateLimit')
@@ -87,6 +88,38 @@ authRouter.post(
   loginTotp,
 )
 
+// ── Email-invite acceptance (public, token-gated) ──────────────────────────
+authRouter.get(
+  '/invite/:token',
+  // #swagger.tags = ['Auth']
+  // #swagger.summary = 'Look up an email invite by token'
+  // #swagger.description = 'Returns the pre-assigned email + role for a valid, pending, unexpired invite so the accept form can render. 404 for anything not currently acceptable.'
+  /* #swagger.responses[200] = { description: 'Invite details', content: { "application/json": { schema: { type: "object", properties: { email: { type: "string" }, role: { type: "string" } } } } } } */
+  /* #swagger.responses[404] = { description: 'Invalid or expired invite', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  param('token').isString().isLength({ min: 8, max: 128 }),
+  validate,
+  getInvite,
+)
+authRouter.post(
+  '/invite/:token/accept',
+  // #swagger.tags = ['Auth']
+  // #swagger.summary = 'Accept an email invite (creates the account at the invited role)'
+  // #swagger.description = 'Creates the website user at the invite’s pre-assigned role and logs them in (sets the session cookie). Bypasses the player_registration gate — the invite is its own authority. Rate limited + honeypot-guarded like registration.'
+  /* #swagger.requestBody = { required: true, content: { "application/json": { schema: { type: "object", required: ["username","password"], properties: { username: { type: "string" }, password: { type: "string" } } } } } */
+  /* #swagger.responses[200] = { description: 'Account created and session issued', content: { "application/json": { schema: { $ref: "#/components/schemas/LoginResponse" } } } } */
+  /* #swagger.responses[400] = { description: 'Validation error', content: { "application/json": { schema: { $ref: "#/components/schemas/ValidationError" } } } } */
+  /* #swagger.responses[404] = { description: 'Invalid or expired invite', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  /* #swagger.responses[409] = { description: 'Username taken or invite already used', content: { "application/json": { schema: { $ref: "#/components/schemas/Error" } } } } */
+  ...loginGuards,
+  registerLimiter,
+  param('token').isString().isLength({ min: 8, max: 128 }),
+  body('username').isString().trim().isLength({ min: 3, max: 32 }),
+  body('password').isString().isLength({ min: 8, max: 64 }),
+  body(HONEYPOT_FIELD).optional(),
+  validate,
+  acceptInvite,
+)
+
 authRouter.post(
   '/logout',
   // #swagger.tags = ['Auth']