Refine Docker stack configuration

- Use mariadb:latest and wordpress:php8.4 floating tags
- Add private registry image name (hub.bundespruefstelle.ch/woocommerce)
- Add restart policies (always for prod, unless-stopped for dev)
- Move .env-dist to project root

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

compose.override.yaml

@@ -1,9 +1,11 @@
 services:
   db:
     container_name: woocommerce-db
+    restart: unless-stopped
 
   wordpress:
     container_name: woocommerce
+    restart: unless-stopped
     volumes:
       - ../wp-bootstrap:/var/www/html/wp-content/themes/wp-bootstrap
       - .:/var/www/html/wp-content/themes/wc-bootstrap