feat: add upload recording modal to class view
- Create upload-recording-modal component with file picker
- Meeting time selector dropdown
- File validation (audio formats, 100MB max)
- Upload to /api/transcriptions with class_id and meeting_time_id
- Modal with overlay, close on click outside or X button
- Disable upload when class is archived
- Reload class data after successful upload
- Upload status indicator (uploading state)
- Error display for failed uploads
💘 Generated with Crush
Co-Authored-By: Crush <crush@charm.land>