fix: remap backend host port 8000 → 8100 to avoid port conflict

Port 8000 is occupied on the host. Backend container still listens
internally on 8000; only the host-side mapping changes to 8100.

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

docker-compose.yml

@@ -26,7 +26,7 @@ services:
     volumes:
       - media_data:/media
     ports:
-      - "8000:8000"
+      - "8100:8000"
     depends_on:
       db:
         condition: service_healthy