Add dedicated payroll export screen with PDF and CSV support

[dhruvi-0406]

Summary

• Added a dedicated Payroll screen accessible from the Home screen header
• Implemented payroll summary generation using selectable date ranges and payroll period types
• Added CSV export support for payroll reports
• Added PDF export support with native share and save functionality
• Improved payroll export workflow for mobile devices by supporting PDF preview and file saving
• Kept the implementation isolated to payroll-related functionality only
• Removed unrelated modifications from previous implementation attempts

Testing

• Verified navigation from Home screen to Payroll screen
• Verified payroll summary generation using multiple date ranges
• Verified PDF export generation and preview functionality
• Verified PDF sharing and saving to Downloads/Google Drive
• Verified CSV export functionality
• Verified linting passes with no errors

Screenshots

Home Screen Payroll Header Icon

Payroll Screen Main UI

Payroll PDF Share Sheet

Payroll PDF Preview

Payroll PDF Save To Downloads

Payroll Export Success