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/static/css/styles.css

@@ -1010,7 +1010,7 @@ button:disabled {
 
 .scripts-grid {
     display: grid;
-    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
+    grid-template-columns: repeat(auto-fill, minmax(min(180px, 100%), 1fr));
     gap: 1rem;
 }
 
@@ -1047,6 +1047,10 @@ button:disabled {
 .script-btn .script-label {
     font-weight: 600;
     font-size: 0.875rem;
+    text-align: center;
+    overflow-wrap: break-word;
+    word-break: break-word;
+    max-width: 100%;
 }
 
 .script-btn .script-description {
@@ -1512,6 +1516,7 @@ button:disabled {
     border-radius: 4px;
     font-size: 0.75rem;
     color: var(--accent);
+    white-space: nowrap;
 }
 
 .action-btn {