refactor: improve thumbnail generation quality and stability

- ThumbnailManager: Optimize queue management to prevent flickering; improve cache size tracking in LRU.
- ImageLoader: Enhance JXL/AVIF decoding limits and threading; add SVG rasterization support.
- ImageLoader: Implement robust WIC fallback for full image decoding when previews are unavailable.
- PreviewExtractor: Add support for extracting JPEG thumbnails from TIFF files (IFD0/IFD1).

Author: justnullname