feat(auth): Active Devices — view/revoke mobile sessions

Adds the self-service device-session surface the mobile-SSO spec requires, on
top of the existing mobile_refresh_tokens store.

- Schema: device_name + last_used_at columns on mobile_refresh_tokens (nullable,
  additive via the ALTER section; seeded to now on insert). With single-use
  rotation each login/refresh inserts a fresh row, so the active row's timestamp
  is the session's last activity, and the label is carried forward on refresh.
- Model: listActiveForUser (one row per live device, no token hash) +
  revokeByIdForUser (ownership-scoped, idempotent).
- GET /auth/me/sessions + DELETE /auth/me/sessions/:id (role-agnostic, behind
  requireAuth). Named distinctly from /auth/me/devices (push endpoints).
- device_name is an optional field on /auth/mobile/login and
  /auth/mobile/sso/exchange so the app can label a device.
- Client: an "Active Devices" panel on the player account page (list + sign a
  device out), plus the PlayerLogin change to honor the mobile SSO bridge's
  { redirect } deep link on a 2FA completion.
- Swagger DeviceSession schema + regenerated spec; 3 controller tests. Full
  server suite green (274); client builds.

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

client/src/api/client.js

@@ -68,6 +68,10 @@ export const api = {
   logout: () => req('/auth/logout', { method: 'POST' }),
   // Public SSO provider discovery — drives the login-page provider buttons.
   authProviders: () => req('/auth/providers'),
+  // Active mobile device sessions (role-agnostic self-service under /auth/me).
+  // List the active ones and revoke a single device by its session id.
+  mySessions: () => req('/auth/me/sessions'),
+  revokeMySession: (id) => req(`/auth/me/sessions/${encodeURIComponent(id)}`, { method: 'DELETE' }),
 
   // ----- public -----
   publicSettings: () => req('/public/settings'),