Refactor: unify Docker build config via build.yml.j2 include

Replaced duplicated inline build definitions in multiple docker-compose.yml.j2
templates with a shared include (roles/docker-container/templates/build.yml.j2).
This ensures consistent use of pull_policy: never and Dockerfile context across
services (Postgres, Bookwyrm, Bridgy Fed, Chess, Confluence, Jira, Moodle,
OpenProject, Pretix, Roulette Wheel, WordPress, XWiki, Simpleicons).

Conversation: https://chatgpt.com/share/68cd8f35-b764-800f-9b00-2c837103d2fb

roles/web-app-roulette-wheel/templates/docker-compose.yml.j2

@@ -1,9 +1,7 @@
 {% include 'roles/docker-compose/templates/base.yml.j2' %}
     application:
         container_name: roulette_application
-        build:
-            context: .
-        pull_policy: never
+{% include 'roles/docker-container/templates/build.yml.j2' %}
         ports:
         - 127.0.0.1:{{ ports.localhost.http[application_id] }}:8080
         restart: {{ DOCKER_RESTART_POLICY }}