feat: implement comprehensive error handling and progress tracking

[Mimansha05]

Add detailed error handling, user-friendly messages, and real-time progress tracking across all services.

FASTAPI BACKEND:

• Add errors.py with ErrorCode enum and custom exception classes
• Add progress.py with ProcessingStatus tracking and RequestTracker
• Update main.py /status endpoint with comprehensive error handling
• Add /progress/{request_id} endpoint for real-time progress monitoring
• Add /health endpoint for service status checks
• Add logging throughout analysis pipeline
• Validate file format, size, and content at each step
• Provide actionable error messages with recovery suggestions
• Track processing progress with estimated time remaining

DJANGO BACKEND:

• Add errors.py with error handlers and response models
• Add validation.py with file format and size validation
• Update api.py /get-upload-url endpoint with validation
• Update /chat-history endpoint with error handling
• Add comprehensive file validation checks
• Provide detailed validation error messages
• Test S3 and Pub/Sub connections
• Add request logging for debugging

FRONTEND:

• Add errorHandling.ts utility library for error parsing and formatting
• Add useApiError.ts custom hooks for error and progress management
• Add ErrorDisplay.tsx component for user-friendly error presentation
• Add ProgressDisplay.tsx component for real-time progress visualization
• Add UploadProgress.tsx component for file upload progress
• Add error severity detection and styling
• Add retryable error detection
• Add expandable suggestions for user guidance

DOCUMENTATION:

• Add BETTER_ERROR_HANDLING.md with comprehensive implementation guide
• Document all error codes and handling strategies
• Provide usage examples and testing guidelines
• Include file structure and future improvements

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