feat: complete Phase 8.3 - recording settings (input gain, mono/stereo, sample rate)

Recording Settings (Phase 8.3):
- Added input gain control (0.0-2.0 with dB display)
- Real-time gain adjustment via GainNode during recording
- Mono/Stereo recording mode selection
- Sample rate matching (44.1kHz, 48kHz, 96kHz)
- Mono conversion averages all channels when enabled
- Recording settings panel shown when track is armed

Components Created:
- RecordingSettings.tsx: Settings panel with gain slider, mono/stereo toggle, sample rate buttons

Components Modified:
- useRecording hook: Added settings state and GainNode integration
- AudioEditor: Pass recording settings to TrackList
- TrackList: Forward settings to Track components
- Track: Show RecordingSettings when armed for recording

Technical Details:
- GainNode inserted between source and analyser in recording chain
- Real-time gain updates via gainNode.gain.value
- AudioContext created with target sample rate
- Mono conversion done post-recording by averaging channels
- Settings persist during recording session

Phase 8 Complete:
- ✅ Phase 8.1: Audio Input
- ✅ Phase 8.2: Recording Controls (punch/overdub)
- ✅ Phase 8.3: Recording Settings
- 📋 Phase 9: Automation (NEXT)

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

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

components/tracks/TrackList.tsx

@@ -7,6 +7,7 @@ import { Track } from './Track';
 import { ImportTrackDialog } from './ImportTrackDialog';
 import type { Track as TrackType } from '@/types/track';
 import { createEffect, type EffectType, EFFECT_NAMES } from '@/lib/audio/effects/chain';
+import type { RecordingSettings } from '@/lib/hooks/useRecording';
 
 export interface TrackListProps {
   tracks: TrackType[];
@@ -25,6 +26,10 @@ export interface TrackListProps {
   recordingTrackId?: string | null;
   recordingLevel?: number;
   trackLevels?: Record<string, number>;
+  recordingSettings?: RecordingSettings;
+  onInputGainChange?: (gain: number) => void;
+  onRecordMonoChange?: (mono: boolean) => void;
+  onSampleRateChange?: (sampleRate: number) => void;
 }
 
 export function TrackList({
@@ -44,6 +49,10 @@ export function TrackList({
   recordingTrackId,
   recordingLevel = 0,
   trackLevels = {},
+  recordingSettings,
+  onInputGainChange,
+  onRecordMonoChange,
+  onSampleRateChange,
 }: TrackListProps) {
   const [importDialogOpen, setImportDialogOpen] = React.useState(false);
 
@@ -167,6 +176,10 @@ export function TrackList({
             isRecording={recordingTrackId === track.id}
             recordingLevel={recordingTrackId === track.id ? recordingLevel : 0}
             playbackLevel={trackLevels[track.id] || 0}
+            recordingSettings={recordingSettings}
+            onInputGainChange={onInputGainChange}
+            onRecordMonoChange={onRecordMonoChange}
+            onSampleRateChange={onSampleRateChange}
           />
         ))}
       </div>