fix: improve effects panel styling with padding and gap

Added padding around effects device rack and gap between effect cards
for better visual integration and spacing.

Changes:
- Added p-3 padding to effects rack container
- Added gap-3 between effect device cards
- Improves visual consistency and readability

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

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

components/tracks/TrackExtensions.tsx

@@ -91,8 +91,8 @@ export function TrackExtensions({
 
         {/* Horizontal scrolling device rack - expanded state */}
         {track.showEffects && (
-          <div className="h-48 overflow-x-auto custom-scrollbar bg-muted/70">
-            <div className="flex h-full">
+          <div className="h-48 overflow-x-auto custom-scrollbar bg-muted/70 p-3">
+            <div className="flex h-full gap-3">
               {track.effectChain.effects.length === 0 ? (
                 <div className="text-xs text-muted-foreground text-center py-8 w-full">
                   No devices. Click + to add an effect.