fix: prevent notification close on skip and background audio stall

- playCurrent: set _trackChanging flag and update media session metadata
  before changing src, so the pause event fired by src-swap does not
  set playbackState='paused' and dismiss the Samsung cover screen notification
- Remove stalled->load() handler that silently paused audio with no recovery
- Error handler now retries regardless of paused state (load() causes paused)
- Add .catch() to audio.play() in playCurrent

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

package.json

@@ -4,9 +4,11 @@
   "scripts": {
     "dev": "vite",
     "build": "vite build",
-    "preview": "vite preview"
+    "preview": "vite preview",
+    "icons": "node scripts/gen-icons.mjs"
   },
   "devDependencies": {
+    "sharp": "^0.34.5",
     "vite": "^5.4.0"
   }
 }