- Add rust_xlsxwriter for Excel export with formatting support
- Add docx-rs for Word document import/export with HTML conversion
- Add PPTX export support with slides, shapes, and text elements
- Refactor sheet module into 7 files (types, formulas, handlers, etc)
- Refactor docs module into 6 files (types, handlers, storage, etc)
- Refactor slides module into 6 files (types, handlers, storage, etc)
- Fix collaboration modules (borrow issues, rand compatibility)
- Add ooxmlsdk dependency for future Office 2021 features
- Fix type mismatches in slides storage
- Update security protection API router type
Features:
- Excel: Read xlsx/xlsm/xls, write xlsx with styles
- Word: Read/write docx with formatting preservation
- PowerPoint: Write pptx with slides, shapes, text
- Real-time collaboration via WebSocket (already working)
- Theme-aware UI with --sentient-* CSS variables
