deploy: Traefik hosts + registry images for shop/admin/api

Publish nginx/API images from CI and deploy on the Pi with
shop.zea.lt, admin.zea.lt, and api.iled.zea.lt.

Co-authored-by: Cursor <cursoragent@cursor.com>

docker/Dockerfile.admin

@@ -0,0 +1,4 @@
+FROM nginx:1.27-alpine
+COPY src/admin/dist/admin/browser /usr/share/nginx/html
+COPY docker/nginx-spa.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80