feat: implement Phase 14 settings & preferences with localStorage persistence

Added comprehensive settings system with 5 categories:
- Recording Settings (existing, integrated)
- Audio Settings (buffer size, sample rate, auto-normalize)
- Editor Settings (auto-save interval, undo limit, snap-to-grid, grid resolution, default zoom)
- Interface Settings (theme, waveform color, font size, default track height)
- Performance Settings (peak/waveform quality, spectrogram toggle, max file size)

Features:
- useSettings hook with localStorage persistence
- Automatic save/load of all settings
- Category-specific reset buttons
- Expanded GlobalSettingsDialog with 5 tabs
- Full integration with AudioEditor
- Settings merge with defaults on load (handles updates gracefully)

Settings are persisted to localStorage and automatically restored on page load.

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

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

components/editor/AudioEditor.tsx

@@ -25,6 +25,7 @@ import { ImportTrackDialog } from '@/components/tracks/ImportTrackDialog';
 import { formatDuration } from '@/lib/audio/decoder';
 import { useHistory } from '@/lib/hooks/useHistory';
 import { useRecording } from '@/lib/hooks/useRecording';
+import { useSettings } from '@/lib/hooks/useSettings';
 import type { EffectType } from '@/lib/audio/effects/chain';
 import {
   createMultiTrackCutCommand,
@@ -89,6 +90,16 @@ export function AudioEditor() {
     setSampleRate,
   } = useRecording();
 
+  // Settings hook
+  const {
+    settings,
+    updateAudioSettings,
+    updateUISettings,
+    updateEditorSettings,
+    updatePerformanceSettings,
+    resetCategory,
+  } = useSettings();
+
   // Multi-track hooks
   const {
     tracks,
@@ -1710,6 +1721,12 @@ export function AudioEditor() {
         onInputGainChange={setInputGain}
         onRecordMonoChange={setRecordMono}
         onSampleRateChange={setSampleRate}
+        settings={settings}
+        onAudioSettingsChange={updateAudioSettings}
+        onUISettingsChange={updateUISettings}
+        onEditorSettingsChange={updateEditorSettings}
+        onPerformanceSettingsChange={updatePerformanceSettings}
+        onResetCategory={resetCategory}
       />
 
       {/* Export Dialog */}