Reduce visualizer latency, tighten UI paddings, fix mobile browser toolbar

- Visualizer: FPS 25→30, chunk_size 2048→1024, smoothing 0.65→0.15
- Beat effect: scale 0.03→0.04, glow range 0.5-0.8→0.4-0.8
- UI: reduce container/section paddings from 2rem to 1rem
- Source name: add ellipsis overflow for long names
- Mobile browser toolbar: use flex-wrap instead of column stack,
  hide "Items per page" label text on small screens

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

media_server/config.py

@@ -118,7 +118,7 @@ class Settings(BaseSettings):
         description="Enable audio spectrum visualizer (requires soundcard + numpy)",
     )
     visualizer_fps: int = Field(
-        default=25,
+        default=30,
         description="Visualizer update rate in frames per second",
         ge=10,
         le=60,