feat(auth): optional HTTP Basic Auth for the whole site

nginx includes auth_enabled.conf, (re)written at container start from
BASIC_AUTH_USER/PASSWORD (htpasswd via apache2-utils). Both set => the site +
/api require a shared login; unset => open (local dev not locked out). Set both
on the Coolify web service to protect the deployment.

docker-compose.yml

@@ -6,6 +6,10 @@ services:
     # would collide with Coolify's own :80 / other apps on the host.
     expose:
       - "80"
+    environment:
+      # Set both on the Coolify app to require a shared login for the whole site.
+      - BASIC_AUTH_USER=${BASIC_AUTH_USER:-}
+      - BASIC_AUTH_PASSWORD=${BASIC_AUTH_PASSWORD:-}
     depends_on:
       - api