fix(infra): make IMGPROXY_URL_MAPPING configurable via environment variables

This ensures that the image proxy correctly maps public domains to internal
Docker hostnames across different environments (testing, staging, production)
without manual configuration of the docker-compose.yml file.

.env.example

@@ -57,6 +57,9 @@ SENTRY_DSN=
 IMAGE_TAG=latest
 TRAEFIK_HOST=klz-cables.com
 ENV_FILE=.env
+# IMGPROXY_URL_MAPPING is used to map public domains to internal Docker hostnames
+# Example for testing: https://testing.klz-cables.com/:http://klz-app:3000/,https://cms.testing.klz-cables.com/:http://klz-cms:8055/
+IMGPROXY_URL_MAPPING=
 
 # ────────────────────────────────────────────────────────────────────────────
 # Varnish Configuration