Updated Dockerfile and compose.yaml

Updated Dockerfile to remove USER line, as that prevents proper file
mapping writing.
Updated compose file to map to /app/data where the database is supposed
to be.

compose.yaml

@@ -3,8 +3,8 @@
     image: freetubesync
     build:
       context: .
-      dockerfile: FreeTubeSync/Dockerfile
+      dockerfile: Dockerfile
     ports:
       - "8080:8080"
     volumes:
-      - ./docker_data:/data
+      - ./docker_data:/app/data