chore(docker): work on compose.yaml; remove debris

compose.yaml

@@ -1,10 +1,4 @@
 services:
-  # fradrive-env:
-  #   image: registry.uniworx.de/fradrive/fradrive/fradrive-env:latest
-    # build: ./docker/fradrive-env
-    # pull_policy: if_not_present
-    # volumes:
-    #   - .:/fradrive-src
   frontend:
     build:
       dockerfile: ./docker/frontend/Dockerfile
@@ -13,7 +7,9 @@ services:
       - &fradrive-mnt "fradrive:/fradrive"
     working_dir: /fradrive
   backend:
-    build: ./docker/backend
+    build:
+      dockerfile: ./docker/backend/Dockerfile
+      context: ./
     volumes:
       - *fradrive-mnt
     working_dir: /fradrive