feat: implement per-track and master effect chains (Option 3)

Architecture:
- Each track now has its own effect chain stored in track.effectChain
- Separate master effect chain for the final mix output
- SidePanel has 3 tabs: Tracks, Track FX, Master FX

Changes:
- types/track.ts: Add effectChain field to Track interface
- lib/audio/track-utils.ts: Initialize effect chain when creating tracks
- lib/hooks/useMultiTrack.ts: Exclude effectChain from localStorage, recreate on load
- components/editor/AudioEditor.tsx:
  - Add master effect chain state using useEffectChain hook
  - Add handlers for per-track effect chain manipulation
  - Pass both track and master effect chains to SidePanel
- components/layout/SidePanel.tsx:
  - Update to 3-tab interface (Tracks | Track FX | Master FX)
  - Track FX tab shows effects for currently selected track
  - Master FX tab shows master bus effects with preset management
  - Different icons for track vs master effects tabs

Note: Effect processing in Web Audio API not yet implemented.
This commit sets up the data structures and UI.

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

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

components/editor/AudioEditor.tsx

@@ -44,17 +44,17 @@ export function AudioEditor() {
     togglePlayPause,
   } = useMultiTrackPlayer(tracks, masterVolume);
 
-  // Effect chain (for selected track)
+  // Master effect chain
   const {
-    chain: effectChain,
-    presets: effectPresets,
-    toggleEffectEnabled,
-    removeEffect,
-    reorder: reorderEffects,
-    clearChain,
-    savePreset,
-    loadPresetToChain,
-    deletePreset,
+    chain: masterEffectChain,
+    presets: masterEffectPresets,
+    toggleEffectEnabled: toggleMasterEffect,
+    removeEffect: removeMasterEffect,
+    reorder: reorderMasterEffects,
+    clearChain: clearMasterChain,
+    savePreset: saveMasterPreset,
+    loadPresetToChain: loadMasterPreset,
+    deletePreset: deleteMasterPreset,
   } = useEffectChain();
 
   // Multi-track handlers
@@ -84,6 +84,48 @@ export function AudioEditor() {
     }
   };
 
+  // Per-track effect chain handlers
+  const handleToggleTrackEffect = (effectId: string) => {
+    if (!selectedTrack) return;
+    const updatedChain = {
+      ...selectedTrack.effectChain,
+      effects: selectedTrack.effectChain.effects.map((e) =>
+        e.id === effectId ? { ...e, enabled: !e.enabled } : e
+      ),
+    };
+    updateTrack(selectedTrack.id, { effectChain: updatedChain });
+  };
+
+  const handleRemoveTrackEffect = (effectId: string) => {
+    if (!selectedTrack) return;
+    const updatedChain = {
+      ...selectedTrack.effectChain,
+      effects: selectedTrack.effectChain.effects.filter((e) => e.id !== effectId),
+    };
+    updateTrack(selectedTrack.id, { effectChain: updatedChain });
+  };
+
+  const handleReorderTrackEffects = (fromIndex: number, toIndex: number) => {
+    if (!selectedTrack) return;
+    const effects = [...selectedTrack.effectChain.effects];
+    const [removed] = effects.splice(fromIndex, 1);
+    effects.splice(toIndex, 0, removed);
+    const updatedChain = {
+      ...selectedTrack.effectChain,
+      effects,
+    };
+    updateTrack(selectedTrack.id, { effectChain: updatedChain });
+  };
+
+  const handleClearTrackChain = () => {
+    if (!selectedTrack) return;
+    const updatedChain = {
+      ...selectedTrack.effectChain,
+      effects: [],
+    };
+    updateTrack(selectedTrack.id, { effectChain: updatedChain });
+  };
+
   // Zoom controls
   const handleZoomIn = () => {
     setZoom((prev) => Math.min(20, prev + 1));
@@ -254,15 +296,20 @@ export function AudioEditor() {
           onUpdateTrack={updateTrack}
           onRemoveTrack={handleRemoveTrack}
           onClearTracks={handleClearTracks}
-          effectChain={effectChain}
-          effectPresets={effectPresets}
-          onToggleEffect={toggleEffectEnabled}
-          onRemoveEffect={removeEffect}
-          onReorderEffects={reorderEffects}
-          onSavePreset={savePreset}
-          onLoadPreset={loadPresetToChain}
-          onDeletePreset={deletePreset}
-          onClearChain={clearChain}
+          trackEffectChain={selectedTrack?.effectChain ?? null}
+          onToggleTrackEffect={handleToggleTrackEffect}
+          onRemoveTrackEffect={handleRemoveTrackEffect}
+          onReorderTrackEffects={handleReorderTrackEffects}
+          onClearTrackChain={handleClearTrackChain}
+          masterEffectChain={masterEffectChain}
+          masterEffectPresets={masterEffectPresets}
+          onToggleMasterEffect={toggleMasterEffect}
+          onRemoveMasterEffect={removeMasterEffect}
+          onReorderMasterEffects={reorderMasterEffects}
+          onSaveMasterPreset={saveMasterPreset}
+          onLoadMasterPreset={loadMasterPreset}
+          onDeleteMasterPreset={deleteMasterPreset}
+          onClearMasterChain={clearMasterChain}
         />
 
         {/* Main canvas area */}