- Add server-side authentication validation for all protected API endpoints
- Create auth utility with requireAuth() function for session validation
- Update CombinedDataRepository to filter data by authenticated user ID
- Add findByUserId() method to CatchRecordRepository for user-specific queries
- Replace client-side userId parameters with server-side session extraction
- Use MongoDB aggregation with $lookup and $expr for secure user filtering
- Return 401 errors for unauthenticated requests
- Fix critical security vulnerability where users could see others' catch records
Fixes: User data isolation bug where one user's catch records were used for everyone
Security: Prevents unauthorized access to other users' Pokemon tracking data