045.04 AV Screen

Description

Create AVCodingScreen in presentation layer with timeline editor and time range selection. Support audio and video playback with transcript sync.

Acceptance Criteria

• [ ] #1 Media player plays audio and video files
• [ ] #2 Timeline displays coded time ranges
• [ ] #3 User can mark time ranges by click-drag
• [ ] #4 Time ranges show code colors
• [ ] #5 Transcript panel syncs with playback position
• [ ] #6 Codes panel integrates for selection
• [ ] #7 Keyboard shortcuts for mark start/end