manifest: pin to 20261103-c53112f

The registry builder is working again (the build pushed cleanly), so
restore the dockerImage pin the portal dropped in f45ca19. Tag carries
the Requests-count fix in app/main.py (commit c53112f).

CloudronManifest.json

@@ -30,5 +30,6 @@
   },
   "manifestVersion": 2,
   "website": "https://inference.coop",
-  "contactEmail": "info@inference.coop"
+  "contactEmail": "info@inference.coop",
+  "dockerImage": "registry.inference.coop/code/member-portal:20261103-c53112f"
 }