feat(ws): WebSocket 核心模块（Hub + Client + PubSub + Handler）

- pkg/ws/message.go: 统一消息协议（Message/Response/PushMessage）
- pkg/ws/hub.go: Hub 连接管理（注册/注销/按 userID 查找/在线计数）
- pkg/ws/client.go: 客户端连接封装（readPump/writePump/心跳 30s）
- pkg/ws/pubsub.go: Redis Pub/Sub 消息路由（按用户频道发布/订阅）
- app/ws/handler.go: WebSocket 升级处理（JWT 认证 + 消息分发）
- app/ws/router.go: GET /ws 路由注册
- app/ws/provider.go: Wire Provider Set
- 更新 provider/router 集成 WebSocket 模块

Made-with: Cursor

backend/go-service/router/router.go

@@ -9,6 +9,7 @@ import (
 	"github.com/echochat/backend/app/admin"
 	"github.com/echochat/backend/app/auth"
 	"github.com/echochat/backend/app/provider"
+	wsApp "github.com/echochat/backend/app/ws"
 	"github.com/echochat/backend/pkg/middleware"
 	"github.com/echochat/backend/pkg/utils"
 	"github.com/gin-gonic/gin"
@@ -32,9 +33,9 @@ func Setup(engine *gin.Engine, app *provider.App) {
 	// --- 各模块路由注册 ---
 	auth.RegisterRoutes(engine, app.AuthController, app.AdminAuthController, jwtAuth)
 	admin.RegisterRoutes(engine, app.UserManageController, jwtAuth)
+	wsApp.RegisterRoutes(engine, app.WSHandler)
 
 	// [未来] im.RegisterRoutes(engine, app.ImController, jwtAuth)
 	// [未来] meeting.RegisterRoutes(engine, app.MeetingController, jwtAuth)
-	// [未来] contact.RegisterRoutes(engine, app.ContactController, jwtAuth)
 	// [未来] notify.RegisterRoutes(engine, app.NotifyController, jwtAuth)
 }