feat: complete Phase 10.3 - master metering with peak/RMS display

Added comprehensive master output level monitoring:
- Created MasterMeter component with dual vertical bars (peak + RMS)
- Implemented real-time level monitoring in useMultiTrackPlayer hook
- Added master analyser node connected to audio output
- Displays color-coded levels (green/yellow/red) based on dB thresholds
- Shows numerical dB readouts for both peak and RMS
- Includes clickable clip indicator with reset functionality
- Integrated into PlaybackControls next to master volume

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

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

components/editor/AudioEditor.tsx

@@ -219,6 +219,10 @@ export function AudioEditor() {
     currentTime,
     duration,
     trackLevels,
+    masterPeakLevel,
+    masterRmsLevel,
+    masterIsClipping,
+    resetClipIndicator,
     play,
     pause,
     stop,
@@ -1056,6 +1060,10 @@ export function AudioEditor() {
           onPunchOutTimeChange={setPunchOutTime}
           overdubEnabled={overdubEnabled}
           onOverdubEnabledChange={setOverdubEnabled}
+          masterPeakLevel={masterPeakLevel}
+          masterRmsLevel={masterRmsLevel}
+          masterIsClipping={masterIsClipping}
+          onResetClip={resetClipIndicator}
         />
       </div>