fix: serialize automation data to prevent DataCloneError

Deep clone automation data using JSON.parse(JSON.stringify()) to remove
any functions before saving to IndexedDB. This prevents DataCloneError
when trying to store non-serializable data.

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

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

lib/storage/projects.ts

@@ -45,21 +45,26 @@ function serializeEffects(effects: any[]): any[] {
  * Convert tracks to serialized format
  */
 function serializeTracks(tracks: Track[]): SerializedTrack[] {
-  return tracks.map(track => ({
-    id: track.id,
-    name: track.name,
-    color: track.color,
-    volume: track.volume,
-    pan: track.pan,
-    muted: track.mute,
-    soloed: track.solo,
-    collapsed: track.collapsed,
-    height: track.height,
-    audioBuffer: track.audioBuffer ? serializeAudioBuffer(track.audioBuffer) : null,
-    effects: serializeEffects(track.effectChain?.effects || []),
-    automation: track.automation,
-    recordEnabled: track.recordEnabled,
-  }));
+  return tracks.map(track => {
+    // Serialize automation by deep cloning to remove any functions
+    const automation = track.automation ? JSON.parse(JSON.stringify(track.automation)) : { lanes: [], showAutomation: false };
+
+    return {
+      id: track.id,
+      name: track.name,
+      color: track.color,
+      volume: track.volume,
+      pan: track.pan,
+      muted: track.mute,
+      soloed: track.solo,
+      collapsed: track.collapsed,
+      height: track.height,
+      audioBuffer: track.audioBuffer ? serializeAudioBuffer(track.audioBuffer) : null,
+      effects: serializeEffects(track.effectChain?.effects || []),
+      automation,
+      recordEnabled: track.recordEnabled,
+    };
+  });
 }
 
 /**