Register chat_backend for django deploy (chat_backend#6 Part B).

Add app_catalog entry, host_apps on adama/roslin/ai-server-4080 (prod
:8003), and document ports/NPM/Postgres/Ollama for active/active.

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

inventory/group_vars/all.yml

@@ -96,6 +96,13 @@ app_catalog:
     # Document root served by nginx and written by `npm run build:<env>`.
     # {env} is replaced with the entry's env (beta/prod).
     webroot_pattern: "/var/www/{env}.chat.aimloperations/html"
+  chat_backend:
+    type: django
+    repo: "{{ git_base_url }}/ai_ml_operations/chat_backend.git"
+    default_branch: master
+    compose_file: docker-compose.prod.yml
+    web_service: web
+    migrate_cmd: "uv run python manage.py migrate --noinput"
 
 # Deploy filter vars. CI passes these; manual runs may leave them undefined
 # to (re)deploy every app listed in the host's host_apps.