chore: Verify proxy requests return 200 OK in browser DevTools

[zigzagdev]

Parent issue

#475

Overview

End-to-end smoke test to confirm the full proxy flow works before closing the parent issue.

Steps

1. Open the heritage list page in a browser
2. Open DevTools → Network tab
3. Filter requests by heritage-image
4. Confirm each request returns status 200 and the response is a valid image

Acceptance criteria

• All GET /api/heritage-image/{id} requests show 200 OK
• Images render correctly in the card grid without falling back to the placeholder
• No CORS or CORP errors appear in the Console tab