feat(session): add session removal endpoint and refactor session management

- Implement new `/sessionMgr/remove` endpoint for superusers to remove sessions
- Refactor session and token management to use sessionTokenMap for better tracking
- Update session cleanup logic to handle both tokens and sessions
- Add documentation for new API endpoint in docs/api.md
- Modify logout handler to use new session removal approach

database.go

@@ -313,6 +313,15 @@ func DBQueryUsers() ([]User, error) { // List all users
 	return users, nil
 }
 
+func DBQuerySpecificUser(userID int) (User, error) { // Query user by ID
+	var user User
+	err := db.QueryRow("SELECT userID, username, type FROM userLogin WHERE userID = ?", userID).Scan(&user.UserID, &user.Username, &user.Type)
+	if err != nil {
+		return user, fmt.Errorf("failed to query user: %w", err)
+	}
+	return user, nil
+}
+
 func DBAddFrpcInstance(instance FrpcInstance) error {
 	_, err := frpcDB.Exec("INSERT INTO frpcInstances (userID, name, serverAddr, serverPort, auth_method, bootAtStart, runUser, configPath, createdAt) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)",
 		instance.UserID, instance.Name, instance.ServerAddr, instance.ServerPort, instance.AuthMethod, instance.BootAtStart, instance.RunUser, instance.ConfigPath, time.Now().Format(time.RFC3339))