fix: ensure track names are strings when loading from localStorage

Added string conversion and error handling when loading tracks from localStorage to prevent corrupted data from causing React rendering errors. If localStorage data is corrupted, it will be cleared automatically.

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

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

lib/hooks/useMultiTrack.ts

@@ -15,11 +15,14 @@ export function useMultiTrack() {
         // Note: AudioBuffers 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
         }));
       }
     } catch (error) {
       console.error('Failed to load tracks from localStorage:', error);
+      // Clear corrupted data
+      localStorage.removeItem(STORAGE_KEY);
     }
 
     return [];