refactor(clickTtPlayerRegistrationService, memberController): improve error handling and diagnostics

- Updated error response structure in memberController to include detailed information instead of a trace array, enhancing clarity for the client.
- Enhanced ClickTtPlayerRegistrationService to capture and return detailed information about the selected search result and last submission attempt, improving error diagnostics.
- Modified frontend to format and display the new detailed error information, providing better context for users during registration failures.

backend/controllers/memberController.js

@@ -225,7 +225,7 @@ const requestClickTtPlayerRegistration = async (req, res) => {
         res.status(error.statusCode || error.status || 500).json({
             success: false,
             error: error.message || 'Click-TT-Antrag konnte nicht eingereicht werden',
-            trace: Array.isArray(error.trace) ? error.trace : []
+            details: error.details || null
         });
     }
 };