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/model/settings/settings.model.js

@@ -11,6 +11,27 @@ const PUBLIC_KEYS = [
   'hero_layout', // portal hero composition (JSON). Draft key stays admin-only.
 ]
 
+// Player self-registration mode. Stored under the 'player_registration' key.
+// NOTE: the raw value is never exposed publicly — getPublic() derives boolean
+// availability flags from it instead (see below).
+const REGISTRATION_KEY = 'player_registration'
+const REGISTRATION_MODES = ['disabled', 'password', 'sso', 'both']
+
+// Resolve the registration mode, defaulting to 'disabled' (and coercing any
+// unexpected stored value back to 'disabled' so a bad row can't open sign-up).
+async function getRegistrationMode() {
+  const value = await settingsDb.get(REGISTRATION_KEY)
+  return REGISTRATION_MODES.includes(value) ? value : 'disabled'
+}
+
+// Derived, public-safe availability flags for the register page.
+function registrationFlags(mode) {
+  return {
+    password: mode === 'password' || mode === 'both',
+    sso: mode === 'sso' || mode === 'both',
+  }
+}
+
 async function get(key) {
   return settingsDb.get(key)
 }
@@ -35,10 +56,26 @@ async function getAll() {
 
 async function getPublic() {
   const all = await getAll()
-  return PUBLIC_KEYS.reduce((acc, key) => {
+  const out = PUBLIC_KEYS.reduce((acc, key) => {
     if (all[key] !== undefined) acc[key] = all[key]
     return acc
   }, {})
+  // Derived registration availability (never the raw mode). Lets the register
+  // page show/hide the password form and SSO buttons.
+  const mode = REGISTRATION_MODES.includes(all[REGISTRATION_KEY]) ? all[REGISTRATION_KEY] : 'disabled'
+  out.registration = registrationFlags(mode)
+  return out
 }
 
-module.exports = { get, set, setMany, getAll, getPublic, PUBLIC_KEYS }
+module.exports = {
+  get,
+  set,
+  setMany,
+  getAll,
+  getPublic,
+  PUBLIC_KEYS,
+  REGISTRATION_KEY,
+  REGISTRATION_MODES,
+  getRegistrationMode,
+  registrationFlags,
+}