feat: add AdjustExistingTrackDrift use case to adjust drift scale of existing tracks

- Implemented AdjustExistingTrackDrift struct with execute method to modify drift scale of existing tracks in a project.
- Added tests for adjusting drift scale, handling non-existent track IDs, and invalid scale values.
- Updated MediaTrackInfo and AudioTrack entities to include drift_scale field.
- Enhanced Project entity with needs_mkvmerge method to determine if mkvmerge is required based on drift scale.
- Integrated drift scale adjustments into existing track list UI, allowing users to modify drift values.
- Updated various use cases and UI components to support drift scale functionality, including add audio/subtitle forms and batch processing.
- Implemented mkvmerge availability check and integrated it into the application workflow for conditional processing.

src/adapters/ffmpeg/command_builder.rs

@@ -310,6 +310,7 @@ mod tests {
             TrackLanguage::new("por").unwrap(),
             false,
             String::new(),
+            1.0,
         )
         .unwrap();
 
@@ -329,6 +330,7 @@ mod tests {
             TrackLanguage::new("por").unwrap(),
             false,
             String::new(),
+            1.0,
         )
         .unwrap();
 
@@ -350,6 +352,7 @@ mod tests {
             TrackLanguage::new("por").unwrap(),
             false,
             String::new(),
+            1.0,
         )
         .unwrap();