docker: add a cache dir writable by docker user

Now required by uv
Refs: #3682

docker-compose.yml

@@ -56,7 +56,7 @@ services:
       - PGPASSWORD=password
       - PYTHONPATH=.
       - ITOU_LOG_LEVEL=DEBUG
-      - ITOU_CACHE=/app/.cache
+      - XDG_CACHE_HOME=/app/.cache
       - CELLAR_ADDON_HOST=minio:${MINIO_PORT_ON_DOCKER_HOST:-9000}
       - VIRTUAL_ENV=/app/.venv-docker
       - REDIS_URL=redis://redis:6379
@@ -73,6 +73,7 @@ services:
     volumes:
       # Mount the current directory into `/app` inside the running container.
       - .:/app
+      - itou_cache:/app/.cache
     restart: unless-stopped
     ports:
       - "127.0.0.1:${DJANGO_PORT_ON_DOCKER_HOST:-8000}:8000"
@@ -86,3 +87,4 @@ services:
 volumes:
   postgres_data:
   itou_minio:
+  itou_cache:

docker/dev/django/Dockerfile

@@ -56,3 +56,4 @@ ENTRYPOINT ["/entrypoint.sh"]
 # Don't use root as default user
 USER $APP_USER
 WORKDIR $APP_DIR
+RUN mkdir -p .cache