fix(email): wire PLATFORM_URL into prod compose, was always falling back to localhost

Set-password links in every password-setup/reset email pointed at
http://localhost:5173 in production because PLATFORM_URL was never mapped
in docker-compose.prod.yml's backend environment block — the app silently
used its dev default. Now defaults to the real domain from CORS_ORIGINS.

docker-compose.prod.yml

@@ -90,6 +90,9 @@ services:
       REDIS_TOKEN_BLACKLIST_DB: ${REDIS_TOKEN_BLACKLIST_DB:-1}
       REDIS_CACHE_DB: ${REDIS_CACHE_DB:-2}
       CORS_ORIGINS: ${CORS_ORIGINS:-}
+      # Base URL used to build links in outbound emails (set-password, etc).
+      # Must be the real public frontend URL, not the dev default.
+      PLATFORM_URL: ${PLATFORM_URL:-http://aegis.undiamagico.es}
       AEGIS_ENV: ${AEGIS_ENV:-production}
       SECURE_COOKIES: ${SECURE_COOKIES:-false}
       ADMIN_USERNAME: ${ADMIN_USERNAME:-admin}