Fix HuggingFace demo video to enable audio with controls

- Remove autoplay and muted attributes to allow audio playback
- Add controls attribute for play/pause, volume, timeline controls
- Add responsive styling for proper display on all screen sizes
- Audio is essential for language learning demo

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

index.html

@@ -928,7 +928,7 @@
 
             <div class="hero-visual">
                 <div class="robot-card">
-                    <video src="docs/assets/language-partner-demo.mp4" alt="Reachy Language Partner demo" autoplay loop muted playsinline></video>
+                    <video src="docs/assets/language-partner-demo.mp4" controls playsinline loop style="max-width: 100%; height: auto;"></video>
                     <p class="robot-caption">✨ Your robot celebrates your progress with dances and expressive motions</p>
                 </div>
             </div>