feat: complete Phase 8.2 - integrate recording into multi-track UI

Completed the integration of recording functionality into the AudioEditor:

Recording Controls:
- Added global record button to PlaybackControls component
- Implemented track arming system (arm track before recording)
- Added visual feedback with pulsing red animations during recording
- Connected recording state from useRecording hook to UI

AudioEditor Integration:
- Added handleToggleRecordEnable for per-track record arming
- Added handleStartRecording with permission checks and toast notifications
- Added handleStopRecording to save recorded audio to track buffer
- Connected recording input level monitoring to track meters

TrackList Integration:
- Pass recording props (onToggleRecordEnable, recordingTrackId, recordingLevel)
- Individual tracks show input level meters when armed or recording
- Visual indicators for armed and actively recording tracks

This completes Phase 8 (Recording) implementation with:
✅ MediaRecorder API integration
✅ Input level monitoring with RMS calculation
✅ Per-track record arming
✅ Global record button
✅ Real-time visual feedback
✅ Permission handling
✅ Error handling with user notifications

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/tracks/TrackList.tsx

@@ -21,6 +21,9 @@ export interface TrackListProps {
   onUpdateTrack: (trackId: string, updates: Partial<TrackType>) => void;
   onSeek?: (time: number) => void;
   onSelectionChange?: (trackId: string, selection: { start: number; end: number } | null) => void;
+  onToggleRecordEnable?: (trackId: string) => void;
+  recordingTrackId?: string | null;
+  recordingLevel?: number;
 }
 
 export function TrackList({
@@ -36,6 +39,9 @@ export function TrackList({
   onUpdateTrack,
   onSeek,
   onSelectionChange,
+  onToggleRecordEnable,
+  recordingTrackId,
+  recordingLevel = 0,
 }: TrackListProps) {
   const [importDialogOpen, setImportDialogOpen] = React.useState(false);
 
@@ -151,6 +157,13 @@ export function TrackList({
                 ? (selection) => onSelectionChange(track.id, selection)
                 : undefined
             }
+            onToggleRecordEnable={
+              onToggleRecordEnable
+                ? () => onToggleRecordEnable(track.id)
+                : undefined
+            }
+            isRecording={recordingTrackId === track.id}
+            recordingLevel={recordingTrackId === track.id ? recordingLevel : 0}
           />
         ))}
       </div>