feat: Add comprehensive test suite for all services and components
- Set up Vitest with testing-library for React component tests
- Add 20 tests for pdfService (field extraction, PDF filling, visual overlay)
- Add 14 tests for geminiService with mocked API responses
- Add 17 tests for FileUpload component (drag-drop, file selection, preview)
- Add 28 tests for ReviewPanel component (rendering, editing, filtering)
- Add 21 Python tests for fill_pdf.py (extraction, filling, CLI)
Total: 100 tests covering critical functionality
https://claude.ai/code/session_01Wi3BtYKgQu6v4zbydtG6Sy
cbacd3430c