feat(ws): A3 WebSocket 统一连接管理 — 心跳/注册表/监控/优雅关闭

- 新增 pkg/wshub/manager.go 统一 WebSocket 连接管理器 (WSManager)
- 6 个 WebSocket handler 全部迁移: WebShell/kubectl/PodExec/Audit/Metrics/Pipeline
- 心跳机制: ping(30s) + pong handler + read deadline(60s) 自动检测死连接
- 连接注册表: 元数据(类型/用户/远程地址/连接时间/最后活跃)
- 每用户连接限制 MaxConnsPerUser=15 防资源耗尽
- 监控端点: GET /api/v1/ws/stats + GET /api/v1/ws/connections
- 优雅关闭: CloseAll() 发送 CloseGoingAway 帧并关闭所有连接
- 消除 3 个重复 websocket.Upgrader 变量统一为 WSManager 内部 upgrader
- 6/6 A3 测试通过, 17/17 回归测试通过

backend/controller/audit_hub.go

@@ -3,23 +3,26 @@ package controller
 
 import (
 	"log"
-	"net/http"
 	"sync"
 
+	"ezops/middleware"
+	"ezops/pkg/wshub"
+
 	"github.com/gin-gonic/gin"
-	"github.com/gorilla/websocket"
 )
 
 // AuditHub 终端审计流中心 — 管理所有活跃会话的审计订阅者
 type AuditHub struct {
 	mu       sync.RWMutex
 	watchers map[uint]map[chan []byte]struct{} // sessionID -> set of watcher channels
+	wsMgr    *wshub.WSManager
 }
 
 // NewAuditHub 创建审计 Hub
-func NewAuditHub() *AuditHub {
+func NewAuditHub(wsMgr *wshub.WSManager) *AuditHub {
 	return &AuditHub{
 		watchers: make(map[uint]map[chan []byte]struct{}),
+		wsMgr:    wsMgr,
 	}
 }
 
@@ -76,20 +79,18 @@ func (h *AuditHub) Cleanup(sessionID uint) {
 	}
 }
 
-var auditUpgrader = websocket.Upgrader{
-	CheckOrigin:     func(r *http.Request) bool { return true },
-	ReadBufferSize:  1024,
-	WriteBufferSize: 1024,
-}
-
 // ServeAuditStream 处理 /ws/audit/:sessionId WebSocket — 实时推送终端输出
 func (h *AuditHub) ServeAuditStream(c *gin.Context, sessionID uint, historyData string, sessionInfo map[string]interface{}) {
-	conn, err := auditUpgrader.Upgrade(c.Writer, c.Request, nil)
+	userID := middleware.GetUserID(c)
+	username := middleware.GetUsername(c)
+
+	conn, info, err := h.wsMgr.Upgrade(c, wshub.TypeAudit, userID, username)
 	if err != nil {
 		log.Printf("[AuditStream] WS 升级失败 session=%d: %v", sessionID, err)
 		return
 	}
-	defer conn.Close()
+	defer h.wsMgr.Unregister(info)
+	h.wsMgr.StartHeartbeat(conn, info)
 
 	// 发送会话元信息
 	conn.WriteJSON(map[string]interface{}{