Homepage: rewrite deploy

Prepare for two-step deploy:
- local build and fix local tag
- deploy to remote server

vars/homepage.yml

@@ -4,4 +4,5 @@ app_user: "{{ app_name }}"
 base_dir: "/home/{{ app_user }}"
 docker_registry_prefix: "cr.yandex/crplfk0168i4o8kd7ade"
 
-homepage_web_image: "{{ homepage_web_image | default(omit) }}"
+# Registry images
+registry_homepage_nginx_image: "{{ (docker_registry_prefix, homepage_nginx_image) | path_join }}"