feat: build headless theatre laboratory website

docs/architecture.md

@@ -1,13 +1,21 @@
 # Architecture
 
-Describe the project architecture here.
+The system has three runtime components on the Docker Compose default network:
 
-Include:
+1. Astro renders the public single page and requests one aggregate JSON document.
+2. Wagtail/Django manages editorial content, serves media in development, and exposes
+   the read-only `/api/site/home/` endpoint.
+3. PostgreSQL persists Wagtail content and metadata.
 
-- main components;
-- runtime dependencies;
-- data flow;
-- persistence;
-- external integrations;
-- deployment topology;
-- relevant ADRs.
+The aggregate response contains `settings`, `homepage`, `feature_cards`, `teacher`,
+`lesson_info`, `shows`, and `gallery_items`. Image values contain browser-facing URLs
+and alternative text. Only published home content and records marked for home display
+are exposed. Astro validates/normalizes the response and falls back to checked-in
+Italian demo content if fetching fails.
+
+Wagtail's authenticated admin remains the only editing interface. The public frontend
+has no database access and no public write API. Uploaded media is stored in a dedicated
+Compose volume.
+
+The deployment topology and content model are recorded in
+[ADR-0001](adr/0001-headless-wagtail-astro.md).