fix: prevent infinite loop in waveform rendering

- Add safety check for duration === 0 (first track scenario)
- Ensure trackWidth doesn't exceed canvas width
- Use Math.floor for integer loop iterations
- Prevent division by zero in samplesPerPixel calculation

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

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

components/tracks/Track.tsx

@@ -341,16 +341,17 @@ export function Track({
     }
 
     // Calculate how much of the canvas width this track's duration occupies
-    const trackDurationRatio = buffer.duration / duration;
-    const trackWidth = width * trackDurationRatio;
-    const samplesPerPixel = buffer.length / trackWidth;
+    // If duration is 0 or invalid, use full width (first track scenario)
+    const trackDurationRatio = duration > 0 ? buffer.duration / duration : 1;
+    const trackWidth = Math.min(width * trackDurationRatio, width);
+    const samplesPerPixel = trackWidth > 0 ? buffer.length / trackWidth : 0;
 
     // Draw waveform
     ctx.fillStyle = track.color;
     ctx.strokeStyle = track.color;
     ctx.lineWidth = 1;
 
-    for (let x = 0; x < trackWidth; x++) {
+    for (let x = 0; x < Math.floor(trackWidth); x++) {
       const startSample = Math.floor(x * samplesPerPixel);
       const endSample = Math.floor((x + 1) * samplesPerPixel);