fix: render customizer images through wordpress media

docs/runbook.md

@@ -35,6 +35,19 @@ HTTPS redirects during production startup.
 2. Run `docker compose --profile tools run --rm wp-cli -c 'wp theme status azionelab'`.
 3. Verify file ownership before changing permissions; never make the tree world-writable.
 
+## Uploaded image does not appear on the public page
+
+1. Confirm the image was selected in **Appearance > Customize**, not only uploaded in
+   **Media**. For the teacher portrait, use **Appearance > Customize > Il maestro >
+   Foto**, then publish the change.
+2. Hard-refresh the browser or purge the CDN cache. An NGINX log status `304` for
+   `/wp-content/uploads/...` is not an application error; it means the browser already
+   has a cached copy and NGINX did not resend the file body.
+3. If the upload appears in Media but not on the page, inspect the generated `<img>`
+   URL and verify it uses the public scheme/host configured by `WP_URL`.
+4. Confirm the uploaded file exists under `WORDPRESS_DATA_PATH/wp-content/uploads` and
+   is readable by the WordPress container user.
+
 ## A service cannot write to its volume
 
 1. Stop the affected service.