Improve docker setup

- add .dockerignore to reduce build context
- add entrypoint.sh to initialize environment before user switch
- fix Celery setting deprecation warnings
- downgrade importlib-metadata for Celery compatibility
- set TZ environment variable for consistent Celery timestamps

gvamysql.sh

@@ -5,7 +5,8 @@ set -e
 QUEUE=mysql
 TASKS=${QUEUE}tasks
 APP=gvamysql
+export TZ="Europe/Berlin"
 
 . "/srv/${APP}/.venv/bin/activate"
 cd /srv/${APP}/${APP}
-celery -A "${TASKS}" worker -Q "${QUEUE}" -l info
+celery -A "${TASKS}" worker -Q "${QUEUE}" -E -l info