remove hardcoded secret key, rely on env variable

docker-compose.yaml

@@ -5,6 +5,7 @@ services:
     restart: always
     environment:
       - SQLITE_DB=database.db
+      - SECRET_KEY=notasecuresecretkeyonlyuseforlocaldevelopment
     volumes:
       - ./database.db:/app/database.db
     ports: