fix: bypass service worker for audio to prevent iOS PWA hangs (#466)

audio streaming was intermittently hanging in iOS standalone (PWA) mode.
the service worker was intercepting /audio/{file_id} requests with
NetworkFirst caching, which caused issues with:
- 307 redirects to R2 CDN getting cached/stale
- range request headers not being handled properly on iOS Safari

switched to NetworkOnly for audio routes so the SW passes through
without interference. we weren't actually caching audio files anyway
(just the redirect response), so there's no functional loss.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <[e-mail]>

frontend/vite.config.ts

···
 				globPatterns: ['**/*.{js,css,html,ico,png,svg,woff2}'],
 				runtimeCaching: [
 					{
+						// audio streaming: bypass SW entirely to avoid iOS PWA hangs
+						// (the redirect to R2 CDN + range requests don't play well with caching)
+						urlPattern: /^https:\/\/api\.plyr\.fm\/audio\/.*/i,
+						handler: 'NetworkOnly'
+					},
+					{
 						urlPattern: /^https:\/\/api\.plyr\.fm\/.*/i,
 						handler: 'NetworkFirst',
 						options: {