fix: add fixed width to fader labels and show 2 decimal places

Added fixed widths to prevent component movement when values change:
- TrackFader: w-[32px] for value display
- MasterFader: w-[36px] for value/peak/RMS display

Changed decimal precision from .toFixed(1) to .toFixed(2) for more
accurate dB readings (e.g., -3.11 instead of -3.1).

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

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

components/tracks/TrackFader.tsx

@@ -163,12 +163,12 @@ export function TrackFader({
       <div className="flex flex-col justify-center items-start text-[9px] font-mono">
         {/* Current dB Value */}
         <div className={cn(
-          'font-bold text-[10px]',
+          'font-bold text-[10px] w-[32px]',
           valueDb > -3 ? 'text-red-500' :
           valueDb > -6 ? 'text-yellow-500' :
           'text-green-500'
         )}>
-          {valueDb > -60 ? `${valueDb.toFixed(1)}` : '-∞'}
+          {valueDb > -60 ? `${valueDb.toFixed(2)}` : '-∞'}
         </div>
       </div>
     </div>