a11y: screen reader and keyboard improvements

- Audio player: aria-labels for Play/Pause, Loop, Mute, Close; labelled playback and volume sliders
- Generation: aria-labels for Generate speech and Fine tune instructions buttons
- Voice cards: focusable, labelled, Enter/Space to select
- History rows: focusable, labelled, Enter/Space to play; transcript textarea labelled
- Voices tab: focusable rows, labelled, Enter/Space to edit; Actions button labelled
- Model management: focusable model rows and labelled Download/Delete buttons
- Server tab: regions with aria-label and tabIndex for Connection, Status, App Updates
- Stories: focusable story rows, labelled, Enter/Space to select; Actions and track editor buttons labelled
- Voice profile samples: Play/Pause/Stop and mini-player slider labelled

Tested with NVDA and Narrator on Windows. See docs/PR-ACCESSIBILITY.md for full description.

Made-with: Cursor

app/src/components/VoiceProfiles/AudioSampleSystem.tsx

@@ -77,7 +77,13 @@ export function AudioSampleSystem({
               </div>
               <p className="text-sm text-muted-foreground text-center">File: {file.name}</p>
               <div className="flex gap-2">
-                <Button type="button" size="icon" variant="outline" onClick={onPlayPause}>
+                <Button
+                  type="button"
+                  size="icon"
+                  variant="outline"
+                  onClick={onPlayPause}
+                  aria-label={isPlaying ? 'Pause' : 'Play'}
+                >
                   {isPlaying ? <Pause className="h-4 w-4" /> : <Play className="h-4 w-4" />}
                 </Button>
                 <Button