feat: add balance display, user columns, device mgmt and sessions for agent
- Backend: add balance to agent stats API
- Backend: return full user details (balance, expiry, online_status, device_count, application) in agent users API
- Backend: export admin device/session handlers, add agent routes for devices and sessions
- Backend: add card type permission check and balance deduction for agent user creation
- Backend: extract checkAgentUserPermission helper, add user edit API
- Frontend: add balance card to agent dashboard
- Frontend: add application, online_status, device_count, balance, expiry_at columns to agent user table
- Frontend: add agent devices page (reuse admin data-table component)
- Frontend: add agent sessions page (reuse admin data-table component)
- Frontend: add devices and sessions to agent navigation and routes
- Add i18n keys for agent devices, sessions, user columns, dashboard balance
admin
853c22fdbe