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.yaml

@@ -1,6 +1,7 @@
 services:
   db:
-    image: mariadb:11
+    image: mariadb:latest
+    restart: always
     volumes:
       - db_data:/var/lib/mysql
     environment:
@@ -15,6 +16,8 @@ services:
       retries: 5
 
   wordpress:
+    image: hub.bundespruefstelle.ch/woocommerce:latest
+    restart: always
     build:
       context: .
       dockerfile: docker/Dockerfile