Release v3.0.0: PDF Viewer & Editor Integration

Major Features:
- Integrated PDF viewer with zoom, page navigation, and fit modes
- PDF editor toolbar with direct access to all PDF operations
- New app branding with docico1.png icon
- ConcreteInfo theme (light & dark variants)
- Comprehensive PDF editing: merge, split, compress, rotate, delete, reorder
- Watermark, encrypt, decrypt, and permissions management
- Overwrite original file option for all PDF operations

UI Improvements:
- PDF viewer takes full screen when active (hides tabs and toolbar)
- Compact modals with reduced font sizes
- Dark theme fixes for icons and dialogs
- Save/Save As options for PDF operations
- Improved PDF toolbar theming

Technical:
- Added isPdfViewerActive state tracking
- Proper PDF document lifecycle management
- Fixed hang issues when switching between PDF and markdown
- All dependencies are open-source (MIT, Apache 2.0, BSD)

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

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

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