[BUG] Audio sync issue with video cuts

[clencyc]

Problem

When users cut/trim video clips, the audio goes out of sync. Audio continues from original timeline instead of trimmed timeline.

Steps to Reproduce

1. Upload a video with audio
2. Trim the video (remove first 10 seconds)
3. Play video - audio is out of sync with video

Expected Behavior

Audio should start from the trim point, not from original position

Current Behavior

Audio is 10 seconds ahead of video

Environment

• Browser: Chrome 125.x
• OS: macOS/Windows
• Video codec: H.264

Possible Root Cause

Audio and video processed separately without syncing trim times

Files to Check

• LiveEditBackend/video_processor.py - video trimming logic
• components/VideoGenerator.tsx - video playback

Solution Ideas

• Ensure audio and video use same trim offset
• Test with FFmpeg: merge video + audio with same timing
• Verify Gemini API returns aligned timestamps

Acceptance Criteria

• Audio stays in sync with video after trim
• Works with different audio/video codecs
• Tested with multiple video durations
• No audio artifacts or pops

Difficulty: Medium

Estimated time: 3-4 hours