feat: add Sonarr support with background scanning and progress tracking

Add Sonarr integration alongside existing Radarr functionality. Implement background ffprobe scanning with ThreadPoolExecutor, progress tracking API, and separate navigation for movies/series. Series are grouped by show with collapsible episodes. Reduce Gunicorn workers to 1, add scan status endpoint, and update README with Sonarr configuration instructions.

docker-compose.yml

@@ -9,17 +9,24 @@ services:
       RADARR_URL: "http://radarr:7878"
       RADARR_API_KEY: "CHANGE_ME"
 
+      # Optional: Sonarr aktivieren (auskommentieren und Werte anpassen)
+      # SONARR_URL: "http://sonarr:8989"
+      # SONARR_API_KEY: "CHANGE_ME"
+
       # Pfad, den Radarr in seiner API meldet:
       RADARR_MEDIA_PATH: "/data/filme"
 
       # Pfad derselben Dateien INNERHALB dieses Containers:
       LOCAL_MEDIA_PATH: "/media/filme"
+      # SONARR_MEDIA_PATH: "/data/serien"
+      # LOCAL_SERIES_PATH: "/media/serien"
 
       DB_PATH: "/data/cache.db"
       LOG_LEVEL: "INFO"
     volumes:
       # Host-Pfad deiner Film-Library -> interner Dashboard-Pfad
       - /nesflix/filme:/media/filme:ro
+      # - /nesflix/serien:/media/serien:ro
       - ./data:/data
     networks:
       - media