Let staff link their own characters + share the game-accounts UI

- Backend: /admin/shard/{link,accounts,roster/:account,vendors/:account} —
  staff self-service, reusing the player/shard controller (it keys off
  req.user.id, so the same handlers serve any logged-in role). Swagger under
  Admin · Account; spec regenerated.
- components/GameAccounts.jsx: the link-prompt + character-roster UI extracted
  into one reusable component parametrized by an api scope and a charTo(serial)
  route builder.
- PlayerCharacters now renders it (player scope → /player/char/:serial).
- Admin: "My Characters" nav item + /admin/characters (AdminCharacters) and
  /admin/characters/:serial (AdminCharacter, in-shell sheet), using the admin
  self-service scope. api.admin.shard.* added.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011qPmpmVH1xGCiZoz9m9vW3

client/src/api/client.js

@@ -214,6 +214,14 @@ export const api = {
     linkedIdentities: () => req('/admin/account/identities'),
     unlinkIdentity: (provider) => req(`/admin/account/identities/${provider}`, { method: 'DELETE' }),
 
+    // ----- game account linking (self-service, staff) -----
+    shard: {
+      link: (code) => req('/admin/shard/link', { method: 'POST', body: { code } }),
+      accounts: () => req('/admin/shard/accounts'),
+      roster: (account) => req(`/admin/shard/roster/${encodeURIComponent(account)}`),
+      vendors: (account) => req(`/admin/shard/vendors/${encodeURIComponent(account)}`),
+    },
+
     // ----- auth providers / SSO config (admin only) -----
     listAuthProviders: () => req('/admin/auth/providers'),
     createAuthProvider: (data) => req('/admin/auth/providers', { method: 'POST', body: data }),