Add Spotify direct API integration for lyrics, ISRC matching, and playlist ordering

Features:
- SpotifyApiClient: Direct Spotify API client using sp_dc session cookie
- SpotifyLyricsService: Fetch synced lyrics from Spotify's color-lyrics API
- SpotifyPlaylistFetcher: Get playlists with correct track ordering and ISRC codes
- SpotifyTrackMatchingService: ISRC-based exact track matching for external providers

Improvements:
- Lyrics endpoint now prioritizes: 1) Jellyfin embedded, 2) Spotify synced, 3) LRCLIB
- Fixed playback progress reporting - removed incorrect body wrapping for Jellyfin API
- Added SpotifyApiSettings configuration model

Security:
- Session cookie and client ID properly masked in startup logs
- All credentials read from environment variables only

allstarr/appsettings.json

@@ -60,5 +60,14 @@
         "Enabled": true
       }
     ]
+  },
+  "SpotifyApi": {
+    "Enabled": false,
+    "ClientId": "",
+    "ClientSecret": "",
+    "SessionCookie": "",
+    "CacheDurationMinutes": 60,
+    "RateLimitDelayMs": 100,
+    "PreferIsrcMatching": true
   }
 }