feat: Remove YouTubeKit, update XPC service product type to .xpc, and add a build phase to copy a standalone Python runtime.

feat(WebMSupport): ensure Fixed GOP with integer FPS normalization for macOS Live Wallpaper compatibility

feat(WebMSupport): enforce keyframe interval with keyint=60 for Live Wallpaper compatibility

chore: update Makefile, README, and appcast for release

feat(UI): update download views and view models for new Python-based downloader

feat(Core): integrate FFmpeg cancellation and improve video services

feat(Helper): improve XPC protocol with download observer for real-time feedback

refactor(Helper): switch from Deno/YTDLP to Python-based downloader

feat(WebMSupport): add remuxing and stop functionality to FFmpeg wrapper

refactor: Refactor app icon assets, add lcms2, Vulkan, and shaderc build dependencies, and update appcast.

build: Bundle dynamic libraries for macOS releases and update the appcast download link.

refactor: Move asset deselection logic to an `onDelete` callback in `CatalogView` and update the appcast download URL.

feat: Enhance custom asset and category deletion with proper cleanup and UI state management, and update appcast download URLs.

refactor: Optimize thumbnail loading in CatalogView using local NSImage with improved placeholders and update appcast release metadata.

feat: add DMG background image and update gitignore to exclude release artifacts and DMG files.