Add JPush (极光推送) integration to enable push notifications for offline users. This includes:
- New jpush client package with API for batch push notifications
- Configuration for jpush (enabled, app_key, master_secret, production mode)
- Updated push service to send messages via JPush when users are offline
- Added PushChatMessage method with do-not-disturb checking
- Integrated push service with chat service to notify offline users of new messages
- Updated deployment workflow with JPush and related environment variables
Add POST /api/v1/admin/setup-super-admin endpoint to initialize the first super admin.
The endpoint can only be used once - after a super admin exists, subsequent requests
are rejected. Requires valid setup_secret configured via APP_SETUP_SECRET environment
variable or setup_secret in config file.
