feat(provisioning): admin game-signup mode setting, invite link option, staff self-create

Follow-ups from live testing:

- Game-account creation is now an admin Settings control (disabled / website /
  hybrid / game) instead of a hidden on/off flag. The site offers creation for
  website+hybrid; help text notes the shard's SignupMode (Bridge.cfg) has the final
  say. game_account_signup setting widened to a 4-value enum + validated on save.
- Invites: the accept link is ALWAYS returned and shown with a Copy button, and a
  "Email the invitation" toggle lets an admin create a link-only invite (no email)
  or email it. Backend takes sendEmail (default true) and always returns acceptUrl.
- Staff can create a game account from their own /admin/characters page too
  (POST /admin/shard/account → the shared createGameAccount controller), so the
  form is reachable in both the player and admin portals.

Note: the admin Houses view (/admin/houses) already worked; the earlier failure
was a stale Vite HMR state for the new route (needs a hard refresh).

Client build clean; server routes load; swagger regenerated.

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

client/src/api/client.js

@@ -177,7 +177,8 @@ export const api = {
     deleteUser: (id) => req(`/admin/users/${id}`, { method: 'DELETE' }),
     // Email invites.
     listInvites: () => req('/admin/invites'),
-    createInvite: (email, role) => req('/admin/invites', { method: 'POST', body: { email, role } }),
+    createInvite: (email, role, sendEmail = true) =>
+      req('/admin/invites', { method: 'POST', body: { email, role, sendEmail } }),
     revokeInvite: (id) => req(`/admin/invites/${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
@@ -260,6 +261,8 @@ export const api = {
       char: (serial) => req(`/admin/shard/char/${encodeURIComponent(serial)}`),
       sales: () => req('/admin/shard/sales'),
       houses: () => req('/admin/shard/houses'), // full registry (admin/moderator)
+      createAccount: (account, password) =>
+        req('/admin/shard/account', { method: 'POST', body: { account, password } }),
     },
 
     // ----- auth providers / SSO config (admin only) -----