fix: update BASE_IMAGES to only include actual registry images

- Keep: alpine (runtime), node (frontend), rust (backend builder)
- Remove: busybox, golang, nginx (not used)
- Remove: postgres, redis (used from Docker Hub, not registry)
- Eliminates warning messages in cleanup logs

apps/registry/retention-script.yaml

@@ -15,14 +15,11 @@ data:
     # (alpine for rust, node variants for frontend/admin, etc.). If any of
     # these are missing the entire build pipeline breaks.
     BASE_IMAGES = {
-        'alpine',
-        'node',
-        'rust',
-        'busybox',
-        'golang',
-        'nginx',
-        'postgres',
-        'redis',
+        'alpine',  # runtime base image
+        'node',    # frontend/admin builder
+        'rust',    # backend builder
+        # Note: postgres/redis are in docker-compose (Docker Hub), not in registry
+        # busybox/golang/nginx are not used
     }
     # Project-image prefix that we DO prune. Anything outside this is sacred.
     PROJECT_PREFIX = 'nxtgauge-'