Add PWA support: installable standalone app with safe area handling

- Service worker, manifest, and SVG icon for PWA installability
- Root /sw.js route for full-scope service worker registration
- Meta tags: theme-color, apple-mobile-web-app, viewport-fit=cover
- Safe area insets for notched phones (container, mini-player, footer, banner)
- Dynamic theme-color sync on light/dark toggle
- Overscroll prevention and touch-action optimization
- Hide mini-player prev/next buttons on small screens
- Updated README with PWA and new feature documentation

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

media_server/main.py

@@ -154,6 +154,15 @@ def create_app() -> FastAPI:
     # Mount static files and serve UI at root
     static_dir = Path(__file__).parent / "static"
     if static_dir.exists():
+        @app.get("/sw.js", include_in_schema=False)
+        async def serve_service_worker():
+            """Serve service worker from root scope for PWA installability."""
+            return FileResponse(
+                static_dir / "sw.js",
+                media_type="application/javascript",
+                headers={"Cache-Control": "no-cache"},
+            )
+
         app.mount("/static", StaticFiles(directory=str(static_dir)), name="static")
 
         @app.get("/", include_in_schema=False)