feat: Proxy UNESCO images through the Laravel backend for reliable display

[zigzagdev]

Overview

Direct browser requests to UNESCO's CDN are blocked by CORS/CORP restrictions in certain environments.
This epic routes all image fetches through our own Laravel backend, eliminating browser-level security constraints entirely.

Sub-issues (all must be closed to consider this done)

• feat: Add proxy route to routes/api.php #470 Add proxy route to routes/api.php
• feat: Implement proxyImage method in HeritageImageController #471 Implement proxyImage in HeritageImageController
• feat: Replace direct UNESCO image URL with backend proxy URL in HeritageCard #472 Replace direct UNESCO URL with proxy URL in HeritageCard
• chore: Verify item.id is correctly passed to the frontend #473 Verify item.id is correctly passed to the frontend
• chore: Verify proxy requests return 200 OK in browser DevTools #474 Verify proxy requests return 200 OK in browser DevTools

Completion definition

All five sub-issues are closed and images render without errors in production.

Background

The browser enforces CORS and CORP policies when fetching cross-origin resources.
Server-to-server HTTP requests (PHP → UNESCO CDN) bypass these restrictions, so wrapping the fetch in a Laravel controller is the most reliable fix.

Related table

world_heritage_site_images