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/go.sum

@@ -48,6 +48,8 @@ github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/google/wire v0.7.0 h1:JxUKI6+CVBgCO2WToKy/nQk0sS+amI9z9EjVmdaocj4=
 github.com/google/wire v0.7.0/go.mod h1:n6YbUQD9cPKTnHXEBN2DXlOp/mVADhVErcMFb0v3J18=
+github.com/gorilla/websocket v1.5.3 h1:saDtZ6Pbx/0u+bgYQ3q96pZgCzfhKXGPqt7kZ72aNNg=
+github.com/gorilla/websocket v1.5.3/go.mod h1:YR8l580nyteQvAITg2hZ9XVh4b55+EU/adAjf1fMHhE=
 github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
 github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
 github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=