refactor(instance): change instance deletion to use ID instead of name

- Update DBRemoveFrpcInstance to use instanceID for deletion
- Modify DeleteInstanceHandler to accept and validate instanceID
- Improve error messages for invalid instanceID format
- Update logging to use instanceID instead of instanceName

database.go

@@ -385,8 +385,8 @@ func DBQueryFrpcInstance(userID int, instanceName string) (FrpcInstance, error)
 	return instance, nil
 }
 
-func DBRemoveFrpcInstance(userID int, instanceName string) error {
-	_, err := frpcDB.Exec("DELETE FROM frpcInstances WHERE userID = ? AND name = ?", userID, instanceName)
+func DBRemoveFrpcInstanceByID(instanceID int) error {
+	_, err := frpcDB.Exec("DELETE FROM frpcInstances WHERE id = ?", instanceID)
 	if err != nil {
 		return fmt.Errorf("failed to delete frpc instance: %w", err)
 	}