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>

lib/audio/track-utils.ts

@@ -4,6 +4,7 @@
 
 import type { Track, TrackColor } from '@/types/track';
 import { DEFAULT_TRACK_HEIGHT, TRACK_COLORS } from '@/types/track';
+import { createEffectChain } from '@/lib/audio/effects/chain';
 
 /**
  * Generate a unique track ID
@@ -33,6 +34,7 @@ export function createTrack(name?: string, color?: TrackColor): Track {
     mute: false,
     solo: false,
     recordEnabled: false,
+    effectChain: createEffectChain(`${trackName} Effects`),
     collapsed: false,
     selected: false,
   };

lib/hooks/useMultiTrack.ts

@@ -1,6 +1,7 @@
 import { useState, useCallback, useEffect } from 'react';
 import type { Track } from '@/types/track';
 import { createTrack, createTrackFromBuffer } from '@/lib/audio/track-utils';
+import { createEffectChain } from '@/lib/audio/effects/chain';
 
 const STORAGE_KEY = 'audio-ui-multi-track';
 
@@ -24,11 +25,12 @@ export function useMultiTrack() {
           return [];
         }
 
-        // Note: AudioBuffers can't be serialized, so we only restore track metadata
+        // Note: AudioBuffers and EffectChains can't be serialized, so we only restore track metadata
         return parsed.map((t: any) => ({
           ...t,
           name: String(t.name || 'Untitled Track'), // Ensure name is always a string
           audioBuffer: null, // Will need to be reloaded
+          effectChain: createEffectChain(`${t.name} Effects`), // Recreate effect chain
         }));
       }
     } catch (error) {
@@ -45,7 +47,7 @@ export function useMultiTrack() {
     if (typeof window === 'undefined') return;
 
     try {
-      // Only save serializable fields, excluding audioBuffer and any DOM references
+      // Only save serializable fields, excluding audioBuffer, effectChain, and any DOM references
       const trackData = tracks.map((track) => ({
         id: track.id,
         name: String(track.name || 'Untitled Track'),
@@ -58,6 +60,7 @@ export function useMultiTrack() {
         recordEnabled: track.recordEnabled,
         collapsed: track.collapsed,
         selected: track.selected,
+        // Note: effectChain is excluded - will be recreated on load
       }));
       localStorage.setItem(STORAGE_KEY, JSON.stringify(trackData));
     } catch (error) {