feat(push): add JPush integration for offline message push

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

internal/config/jpush.go

@@ -0,0 +1,8 @@
+package config
+
+type JPushConfig struct {
+	Enabled     bool   `mapstructure:"enabled"`
+	AppKey      string `mapstructure:"app_key"`
+	MasterSecret string `mapstructure:"master_secret"`
+	Production  bool   `mapstructure:"production"`
+}