feat: add pluggable music service architecture with Qobuz support

.env.example

@@ -4,7 +4,11 @@ SUBSONIC_URL=http://localhost:4533
 # Path where downloaded songs will be stored on the host
 DOWNLOAD_PATH=./downloads
 
-# Deezer ARL token (required)
+# Music service to use: Deezer or Qobuz (default: Deezer)
+MUSIC_SERVICE=Deezer
+
+# ===== DEEZER CONFIGURATION =====
+# Deezer ARL token (required if using Deezer)
 # See README.md for instructions on how to get this token
 DEEZER_ARL=your-deezer-arl-token
 
@@ -15,10 +19,26 @@ DEEZER_ARL_FALLBACK=
 # If not specified, the highest available quality for your account will be used
 DEEZER_QUALITY=
 
+# ===== QOBUZ CONFIGURATION =====
+# Qobuz user authentication token (required if using Qobuz)
+# Get this from your browser after logging into play.qobuz.com
+# See README.md for detailed instructions
+QOBUZ_USER_AUTH_TOKEN=
+
+# Qobuz user ID (required if using Qobuz)
+# Get this from your browser after logging into play.qobuz.com
+QOBUZ_USER_ID=
+
+# Preferred audio quality: FLAC, FLAC_24_HIGH, FLAC_24_LOW, FLAC_16, MP3_320 (optional)
+# If not specified, the highest available quality will be used
+QOBUZ_QUALITY=
+
+# ===== GENERAL SETTINGS =====
 # Explicit content filter (optional, default: All)
 # - All: Show all tracks (no filtering)
 # - ExplicitOnly: Exclude clean/edited versions, keep original explicit content
 # - CleanOnly: Only show clean content (naturally clean or edited versions)
+# Note: This only works with Deezer, Qobuz doesn't expose explicit content flags
 EXPLICIT_FILTER=All
 
 # Download mode (optional, default: Track)