feat(provisioning): provisioning UI — signup, invites, accept page, unlink

Phase 6: the UI for the Phase 5 provisioning backend.

- CreateGameAccountForm: reusable game-account form (own username + password),
  mapping the sidecar errors (409/429/403/503) to friendly messages. Wired into
  GameAccounts (self-serve) — shown alongside the [link flow when the
  game_account_signup flag is on (exposed via public settings), so a registered
  player can create + link a game account from their portal.
- Admin Invites view (/admin/invites, admin-only): send an invite at a chosen
  access level, list invites with status, revoke pending ones. When email isn't
  configured the create response's accept link is surfaced to copy manually.
- Public accept page (/invite/:token): validates the invite, sets username +
  password (email + role pre-assigned), creates the account at that role and logs
  in; for a player invite it then offers the built-in "create game account" step
  before the portal. Honeypot-guarded like registration.
- Admin unlink wired into UserDetail via GameAccounts (per-account Unlink button,
  confirm + reconcile).
- Backend: expose gameAccountSignup availability in public settings.

Client build clean; server 193/193.

Refs .plans/protocol2-integration.md (Phase 6). Completes the Protocol 2.0/2.1 integration.

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

client/src/api/client.js

@@ -48,6 +48,10 @@ export const api = {
   // optional email. Returns { user } and sets the session cookie on success.
   register: (username, password, extra = {}) =>
     req('/auth/register', { method: 'POST', body: { username, password, ...extra } }),
+  // Email invites (public, token-gated accept).
+  getInvite: (token) => req(`/auth/invite/${encodeURIComponent(token)}`),
+  acceptInvite: (token, username, password, extra = {}) =>
+    req(`/auth/invite/${encodeURIComponent(token)}/accept`, { method: 'POST', body: { username, password, ...extra } }),
   loginTotp: (challenge, code) =>
     req('/auth/login/totp', { method: 'POST', body: { challenge, code } }),
   // Second factor for an SSO login (challenge is held in an httpOnly cookie set by
@@ -171,6 +175,10 @@ export const api = {
     createUser: (data) => req('/admin/users', { method: 'POST', body: data }),
     updateUser: (id, data) => req(`/admin/users/${id}`, { method: 'PUT', body: data }),
     deleteUser: (id) => req(`/admin/users/${id}`, { method: 'DELETE' }),
+    // Email invites.
+    listInvites: () => req('/admin/invites'),
+    createInvite: (email, role) => req('/admin/invites', { method: 'POST', body: { email, role } }),
+    revokeInvite: (id) => req(`/admin/invites/${id}`, { method: 'DELETE' }),
     // A single user's shard (uo-link) footprint, scoped to their linked accounts.
     // accounts/sales/houses/online are user-scoped endpoints; roster/vendors/char
     // reuse the admin-bypass /admin/shard/* endpoints (which already read any
@@ -184,6 +192,7 @@ export const api = {
       houses: () => req(`/admin/users/${id}/shard/houses`),
       online: () => req(`/admin/users/${id}/shard/online`),
       standing: () => req(`/admin/users/${id}/shard/standing`),
+      unlink: (account) => req(`/admin/users/${id}/shard/link/${encodeURIComponent(account)}`, { method: 'DELETE' }),
     }),
 
     // ----- moderation dashboard (admin + moderator) -----
@@ -313,6 +322,8 @@ export const api = {
       vendors: (account) => req(`/player/shard/vendors/${encodeURIComponent(account)}`),
       char: (serial) => req(`/player/shard/char/${encodeURIComponent(serial)}`),
       sales: () => req('/player/shard/sales'),
+      createAccount: (account, password) =>
+        req('/player/shard/account', { method: 'POST', body: { account, password } }),
     },
   },
 }