perf: improve audio streaming, font loading, and video provider timeouts

- Fix audio route content-type handling by using HeadObject metadata first
- Add JetBrains Mono font optimization with display:swap and preload
- Add blur placeholder to video card thumbnails for improved loading
- Fix YouTube API loading with proper state tracking to prevent race conditions
- Simplify timeout handling in YouTube and Vimeo providers using AbortSignal.timeout

app/layout.tsx

@@ -7,6 +7,8 @@ import "./globals.css";
 const jetbrainsMono = JetBrains_Mono({
   subsets: ['latin'],
   variable: '--font-sans',
+  display: 'swap',
+  preload: true,
 });
 
 export const metadata: Metadata = {