fix: resolve JSON parsing error and standardize HTTP client usage

- Fix JSON parsing error in getOrCreateGiteaOrg function (#19)
  - Add content-type validation before JSON parsing
  - Add response cloning for better error debugging
  - Enhance error messages with actual response content
  - Add comprehensive logging for troubleshooting

- Standardize HTTP client usage across codebase
  - Create new http-client.ts utility with consistent error handling
  - Replace all superagent calls with fetch-based functions
  - Replace all axios calls with fetch-based functions
  - Remove superagent, axios, and @types/superagent dependencies
  - Update tests to mock new HTTP client
  - Maintain backward compatibility

- Benefits:
  - Smaller bundle size (removed 3 HTTP client libraries)
  - Better performance (leveraging Bun's optimized fetch)
  - Consistent error handling across all HTTP operations
  - Improved debugging with detailed error messages
  - Easier maintenance with single HTTP client pattern

src/components/activity/ActivityLog.tsx

@@ -313,7 +313,6 @@ export function ActivityLog() {
       setIsInitialLoading(true);
       setShowCleanupDialog(false);
 
-      // Use fetch directly to avoid potential axios issues
       const response = await fetch('/api/activities/cleanup', {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },