Media Sort Alpha 6

Changes since alpha.5:

Theme system:

• Replaced dark mode toggle with a theme picker supporting all 22 built-in iced themes

Thumbnail pipeline:

• Debounced, interruptible thumbnail loading with viewport tracker, which means that only visible grid entries request thumbnails
• SIMD-accelerated fast_image_resize replaces image::thumbnail for faster preview generation

Image format support:

• Auto-detect native image extensions from image::ImageFormat::all() at build time

Platform integration:

• Windows: windows_subsystem attribute and embedded icon resource
• Linux: desktop file integration and Wayland application_id (cfg-gated to Linux only)

Fixes:

• Fix video-params query (video-out-params → video-params) and disable video-rotate
• Prevent mp_image_crop assertion crash when switching videos rapidly
• Don't prematurely stop background scan on empty channel
• Improve WPF settings migration by extending key mapping, also remove dead AnimateGifThumbnails
• Fix release workflow: surgically modify vpk-generated desktop file with sed (preserves vendor metadata, no duplicates)

Cleanup:

• Remove vestigial Rust JSON config migration