Minor change to Architecture header and alt text

Author: chriscarrollsmith

docs/architecture.qmd

@@ -2,7 +2,7 @@
 title: "Architecture"
 ---
 
-## Architecture
+## Data flow
 
 This application uses a Post-Redirect-Get (PRG) pattern. The user submits a form, which sends a POST request to a FastAPI endpoint on the server. The database is updated, and the user is redirected to a GET endpoint, which fetches the updated data and re-renders the Jinja2 page template with the new data.
 
@@ -39,6 +39,6 @@ dot.edge('F', 'G')
 dot.render('static/webapp_flow', format='png', cleanup=True)
 ```
 
-![Webapp Flow](static/webapp_flow.png)
+![Data flow diagram](static/webapp_flow.png)
 
 The advantage of the PRG pattern is that it is very straightforward to implement and keeps most of the rendering logic on the server side. The disadvantage is that it requires an extra round trip to the database to fetch the updated data, and re-rendering the entire page template may be less efficient than a partial page update on the client side.