Implemented clear_all_completed_downloads in YouTubeClient to remove completed, cancelled, errored, and aborted downloads from memory. Updated DownloadOrchestrator to call this method, ensuring both Soulseek and YouTube completed downloads are cleared.
Introduces a DownloadOrchestrator class to route downloads between Soulseek and YouTube based on user-configurable modes (Soulseek only, YouTube only, Hybrid with fallback). Updates web server and UI to support new download source settings, including hybrid mode options and YouTube confidence threshold. Refactors YouTube client for thread-safe download management and bot detection bypass. Ensures quality filtering is skipped for YouTube results and improves file matching and post-processing logic for YouTube downloads.
