fix: serialize effects properly to avoid DataCloneError

Effects contain non-serializable data like functions and audio nodes that
cannot be stored in IndexedDB. Added proper serialization.

Changes:
- Added serializeEffects function to strip non-serializable data
- Uses JSON parse/stringify to deep clone parameters
- Preserves effect type, name, enabled state, and parameters
- Fixes DataCloneError when saving projects with effects

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

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

lib/storage/projects.ts

@@ -27,6 +27,20 @@ export function generateProjectId(): string {
   return `project_${Date.now()}_${Math.random().toString(36).substr(2, 9)}`;
 }
 
+/**
+ * Serialize effects by removing any non-serializable data (functions, nodes, etc.)
+ */
+function serializeEffects(effects: any[]): any[] {
+  return effects.map(effect => ({
+    id: effect.id,
+    type: effect.type,
+    name: effect.name,
+    enabled: effect.enabled,
+    expanded: effect.expanded,
+    parameters: effect.parameters ? JSON.parse(JSON.stringify(effect.parameters)) : undefined,
+  }));
+}
+
 /**
  * Convert tracks to serialized format
  */
@@ -42,7 +56,7 @@ function serializeTracks(tracks: Track[]): SerializedTrack[] {
     collapsed: track.collapsed,
     height: track.height,
     audioBuffer: track.audioBuffer ? serializeAudioBuffer(track.audioBuffer) : null,
-    effects: track.effectChain?.effects || [],
+    effects: serializeEffects(track.effectChain?.effects || []),
     automation: track.automation,
     recordEnabled: track.recordEnabled,
   }));