Player accounts backend: schema, registration, self-service, SSO provision

- Widen users.role enum to include 'player'; make password_hash nullable;
  add email/email_verified/status/last_login_ip; pin username _ci collation.
- POST /auth/register (honeypot + registerLimiter + botScore, reserved-name
  blocklist, duplicate->409, auto-login). player_registration setting gates it.
- SSO auto-provision in finishLogin (setting-gated); return/portal-aware SSO
  redirects for the player portal; status refusal on login + requireAuth.
- New /player self-service group (account, change username/password, TOTP,
  identities), reusing account.controller; accountChangeLimiter.
- Admin: 'player' role + status/email on user create/update, role/status audit,
  player_registration enum validation, derived public registration flags.
- usernamePolicy module (reserved, sanitize, derive, dedup) + unit tests;
  extend SSO callback tests. 133 server tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019rao86n5cXpwAyjdBFEshV

server/src/middleware/rateLimit.js

@@ -24,6 +24,26 @@ const loginLimiter = makeLimiter({
   message: 'Too many login attempts. Please try again later.',
 })
 
+// Public self-registration. Mirrors the login cap: a handful of legitimate
+// attempts per window, a flood is abuse. The global botScore guard + honeypot
+// cover the rest.
+const registerLimiter = makeLimiter({
+  windowMs: 15 * 60 * 1000,
+  max: 10,
+  label: 'register',
+  message: 'Too many registration attempts. Please try again later.',
+})
+
+// Authenticated self-service credential changes (username / password). Tighter
+// than login — a signed-in player rarely changes these, and the wrong-current-
+// password path also feeds the shared login backoff (see the controller).
+const accountChangeLimiter = makeLimiter({
+  windowMs: 15 * 60 * 1000,
+  max: 10,
+  label: 'account-change',
+  message: 'Too many changes. Please try again later.',
+})
+
 // Throttle the public contact form.
 const contactLimiter = makeLimiter({
   windowMs: 60 * 60 * 1000,
@@ -51,4 +71,11 @@ const ssoStartLimiter = makeLimiter({
   message: 'Too many sign-in attempts. Please try again later.',
 })
 
-module.exports = { loginLimiter, contactLimiter, mobileRefreshLimiter, ssoStartLimiter }
+module.exports = {
+  loginLimiter,
+  registerLimiter,
+  accountChangeLimiter,
+  contactLimiter,
+  mobileRefreshLimiter,
+  ssoStartLimiter,
+}