Bug Report & Feature Request: Backdrop Theme Videos & Music Playback Behavior

Issue A: Theme Videos Ignored in Random Mode Behavior: When the "Theme and Trailer Order" setting is set to Random, Jellywatch only plays theme music and completely ignores theme videos. Expected Behavior: Random mode should select randomly from all available theme assets, including theme videos. Issue B: Simultaneous Playback of Video and Music (Audio Conflict, Desync & Performance Drop) Behavior: When both a theme video and theme music are available, Jellywatch attempts to play both at the same time. It mutes the theme video's audio and plays the standalone theme music over it. Audio Desync: Even when the theme video and theme music files have identical filenames, identical runtimes, and identical audio tracks, there is still roughly a 1-second synchronization offset between the playing video and the theme audio track. Impact: This creates an awkward, out-of-sync viewing experience and causes playback stuttering/lag on lower-powered client devices due to decoding two media streams simultaneously. Expected Behavior: Jellywatch should only play one media stream at a time. 2. Feature & Setting Suggestions Media Selection & Prioritization (Jellyfin-Style): Toggle / Preference Setting: Add an explicit setting to enable or disable theme videos and theme music independently, or set a primary media preference (e.g., Prefer Theme Videos over Theme Music). Strict Type Isolation: If a preference is set (e.g., Prefer Theme Videos) and an item contains the preferred media type, Jellywatch should only play that preferred type. Once all available theme videos finish playing, it should not start playing theme music afterward. Theme music should only play as a fallback if no theme videos exist for that item (or vice versa). Unified Volume Setting: Update the existing "Theme Songs" volume control (Off / Low / Med / High) so that it manages the audio volume for both theme music and theme videos.