feat: notification nav + ABS search + HTML desc fix + brighter NowPlaying bg

- Notification sheet: add 'Zum Album →' / 'Öffnen →' button; tapping searches
  Navidrome and navigates to the matching album/playlist
- AppNotification: add navType/navAlbum/navArtist/navId fields (mirrors web notify.js)
- ImporterViewModel: store resolved album/artist/type in notification after download
- ABS Android: search bar with 400ms debounce, server-side search via /search endpoint
- AbsClient: add searchLibraryItems() for library-specific search
- AbsScreen/abs.js: strip HTML tags from book descriptions (<p> tags no longer visible)
- NowPlayingScreen: vibrant palette swatch + lighter scrim (0.15) + wider gradient
  for more visible dominant color background

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

android/app/build.gradle.kts

@@ -96,6 +96,9 @@ dependencies {
     // Palette (dominant cover color extraction in NowPlaying)
     implementation("androidx.palette:palette-ktx:1.0.0")
 
+    // MediaStyle for ABS notification (already transitive via media3-session, made explicit)
+    implementation("androidx.media:media:1.7.0")
+
     // Google Fonts (Outfit)
     implementation(libs.compose.ui.google.fonts)
 }