feat: spotify playlist injection

- Add SpotifyImportSettings configuration model
- Create SpotifyMissingTracksFetcher background service
- Inject virtual Spotify playlists into search results
- Auto-match tracks from external providers
- Update README with feature documentation
- Configure sync window and playlist settings

.env.example

@@ -95,3 +95,36 @@ STORAGE_MODE=Permanent
 # Based on last access time (updated each time the file is streamed)
 # Cache location: /tmp/allstarr-cache (or $TMPDIR/allstarr-cache if TMPDIR is set)
 CACHE_DURATION_HOURS=1
+
+# ===== SPOTIFY PLAYLIST INJECTION (JELLYFIN ONLY) =====
+# REQUIRES: Jellyfin Spotify Import Plugin (https://github.com/Viperinius/jellyfin-plugin-spotify-import)
+# This feature injects virtual Spotify playlists (Release Radar, Discover Weekly) into Jellyfin
+# with tracks auto-matched from external providers (SquidWTF, Deezer, Qobuz)
+
+# Enable Spotify playlist injection (optional, default: false)
+SPOTIFY_IMPORT_ENABLED=false
+
+# Jellyfin server URL (required if SPOTIFY_IMPORT_ENABLED=true)
+# Should match your JELLYFIN_URL unless using a different URL for plugin access
+SPOTIFY_IMPORT_JELLYFIN_URL=http://localhost:8096
+
+# Jellyfin API key (REQUIRED if SPOTIFY_IMPORT_ENABLED=true)
+# Get from Jellyfin Dashboard > API Keys > Create new key
+# This is used to fetch missing tracks files from the Spotify Import plugin
+SPOTIFY_IMPORT_API_KEY=
+
+# Sync schedule: When does the Spotify Import plugin run?
+# Set these to match your plugin's sync schedule in Jellyfin
+# Example: If plugin runs daily at 4:15 PM, set HOUR=16 and MINUTE=15
+SPOTIFY_IMPORT_SYNC_START_HOUR=16
+SPOTIFY_IMPORT_SYNC_START_MINUTE=15
+
+# Sync window: How long to search for missing tracks files (in hours)
+# The fetcher will check every 5 minutes within this window
+# Example: If plugin runs at 4:15 PM and window is 2 hours, checks from 4:00 PM to 6:00 PM
+SPOTIFY_IMPORT_SYNC_WINDOW_HOURS=2
+
+# Playlists to inject (comma-separated, optional)
+# Available: Release Radar, Discover Weekly
+# Leave empty to disable all, or specify which ones to enable
+SPOTIFY_IMPORT_PLAYLISTS=Release Radar,Discover Weekly