- Complete Phase 4: Async API support and batch operations
- Async methods for document loading, rendering, and saving
- Batch operations for page retrieval and deletion
- All annotation support (Phase 1) complete
- Upgraded to .NET 10.0
- Based on PDFium 145.0.7578.0

Features:
- Asynchronous document operations with CancellationToken support
- Batch page operations (GetPages, DeletePages)
- Complete annotation API (highlight, text, stamp annotations)
- SkiaSharp integration for image rendering
- Comprehensive demo application