On-demand audio visualizer capture + UI fixes

- Audio capture starts only when first client subscribes,
  stops when last client unsubscribes (saves CPU/battery)
- Add lifecycle lock to AudioAnalyzer for thread-safe start/stop
- Status badge uses local visualizer state instead of server flag
- Fix script name vertical text break on narrow screens
- Fix script grid minimum column width on small viewports

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

media_server/routes/media.py

@@ -305,15 +305,9 @@ async def set_visualizer_device(
     device_name = request.get("device_name")
     analyzer = get_audio_analyzer()
 
-    # Restart with new device
-    was_running = analyzer.running
+    # set_device() handles stop/start internally if capture was running
     success = analyzer.set_device(device_name)
 
-    # Restart audio broadcast if needed
-    if was_running and success and analyzer.running:
-        await ws_manager.stop_audio_monitor()
-        await ws_manager.start_audio_monitor(analyzer)
-
     return {
         "success": success,
         "current_device": analyzer.current_device,