feat(user): add user type modification endpoint

- Implement new endpoint `/userMgr/modifyType` for updating user types
- Add database function DBUpdateUserType to handle type updates
- Include request validation and proper error handling
- Update API documentation with new endpoint details

database.go

@@ -346,6 +346,14 @@ func DBQuerySpecificUser(userID int) (User, error) { // Query user by ID
 	return user, nil
 }
 
+func DBUpdateUserType (userID int, newType string) error {
+	_, err := db.Exec("UPDATE userLogin SET type = ? WHERE userID = ?", newType, userID)
+	if err != nil {
+		return fmt.Errorf("failed to update user type: %w", err)
+	}
+	return nil
+}
+
 func DBAddFrpcInstance(instance FrpcInstance) error {
 	_, err := frpcDB.Exec("INSERT INTO frpcInstances (userID, name, bootAtStart, runUser, configPath, createdAt) VALUES (?, ?, ?, ?, ?, ?)",
 		instance.UserID, instance.Name, instance.BootAtStart, instance.RunUser, instance.ConfigPath, time.Now().Format(time.RFC3339))