Refactor and enhance export functionality with Team Hours support

- Fix missing import statements for CSV/Excel export functionality
- Refactor export code into modular helper functions for better maintainability
- Add comprehensive Team Hours export feature with CSV and Excel support
- Enhance export UI styling with modern gradients and hover effects
- Add role-based access control for team export functionality
- Include date range filtering and team leader inclusion options
- Add proper error handling and user feedback for export operations
- Update dependencies to include pandas and xlsxwriter
- Fix JavaScript scope issues for export button functionality

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

requirements.txt

@@ -9,3 +9,6 @@ SQLAlchemy==1.4.23
 python-dotenv==0.19.0
 pyotp==2.6.0
 qrcode[pil]==7.3.1
+pandas==1.5.3
+xlsxwriter==3.1.2
+Flask-Mail==0.9.1