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/webshell.go

@@ -15,9 +15,14 @@ import (
 	"golang.org/x/crypto/ssh"
 	"gorm.io/gorm"
 
+	"ezops/middleware"
 	"ezops/model"
+	"ezops/pkg/wshub"
 )
 
+// upgrader is kept for backward compatibility (k8s_pod.go/kubectl_shell.go reference it).
+// The WSManager has its own internal upgrader; this global is aliased for handlers
+// that haven't been migrated yet or need low-level access.
 var upgrader = websocket.Upgrader{
 	CheckOrigin: func(r *http.Request) bool {
 		return true
@@ -87,11 +92,12 @@ func (r *asciicastRecorder) Len() int       { return r.buf.Len() }
 type WebShellHandler struct {
 	db       *gorm.DB
 	auditHub *AuditHub
+	wsMgr    *wshub.WSManager
 	clients  sync.Map // sessionID → *SessionContext
 }
 
-func NewWebShellHandler(db *gorm.DB, auditHub *AuditHub) *WebShellHandler {
-	return &WebShellHandler{db: db, auditHub: auditHub}
+func NewWebShellHandler(db *gorm.DB, auditHub *AuditHub, wsMgr *wshub.WSManager) *WebShellHandler {
+	return &WebShellHandler{db: db, auditHub: auditHub, wsMgr: wsMgr}
 }
 
 // KillSession 强制终止指定终端会话
@@ -148,21 +154,23 @@ func (h *WebShellHandler) Terminal(c *gin.Context) {
 		return
 	}
 
-	conn, err := upgrader.Upgrade(c.Writer, c.Request, nil)
+	// Extract user identity BEFORE upgrade (needed for WSManager registration).
+	userID := middleware.GetUserID(c)
+	username := middleware.GetUsername(c)
+
+	conn, info, err := h.wsMgr.Upgrade(c, wshub.TypeTerminal, userID, username)
 	if err != nil {
 		log.Printf("[WebShell] WS upgrade failed: %v", err)
 		return
 	}
-	defer conn.Close()
+	defer h.wsMgr.Unregister(info)
+	h.wsMgr.StartHeartbeat(conn, info)
 
 	var userIDPtr *uint
-	if uid, exists := c.Get("userID"); exists {
-		if uidVal, ok := uid.(uint); ok {
-			userIDPtr = &uidVal
-		}
+	if userID > 0 {
+		userIDPtr = &userID
 	}
-	username, _ := c.Get("username")
-	usernameStr, _ := username.(string)
+	usernameStr := username
 
 	termSession := model.TerminalSession{
 		UserID:     userIDPtr,