feat(transcoding): add FFmpeg HLS transcoding support

- Introduced `TranscodeManager` for managing on-demand transcoding of local video files.
- Added configuration options for transcoding in `Config` and `LocalFilesConfig`.
- Implemented new API routes for managing transcoding settings, stats, and cache.
- Updated `LocalFilesProvider` to support transcoding capabilities.
- Created frontend components for managing transcode settings and displaying stats.
- Added database migration for transcode settings.
- Enhanced existing routes and DTOs to accommodate new transcoding features.

k-tv-backend/infra/src/local_files/mod.rs

@@ -2,7 +2,9 @@ pub mod config;
 pub mod index;
 pub mod provider;
 pub mod scanner;
+pub mod transcoder;
 
 pub use config::LocalFilesConfig;
 pub use index::LocalIndex;
 pub use provider::{LocalFilesProvider, decode_stream_id};
+pub use transcoder::TranscodeManager;