manifest: build on-server (drop the registry image pin)

The remote registry builder is currently unusable from this Cloudron host:
its in-build `docker login registry.inference.coop` resolves the registry to
127.0.0.1:443 and is refused, so no new image can be pushed to the registry
(the box's own docker CAN reach the registry — a pull of a missing tag returns
a clean 404 — so this is the builder's container network, not the registry).
The panel and dashboard are already unpinned and build on-server via
`cloudron update` from the repo dir; the portal joins them so its code can ship
the operator-spend breakout the dashboard reads. Restore the pin when the
builder is fixed.

CloudronManifest.json

@@ -30,6 +30,5 @@
   },
   "manifestVersion": 2,
   "website": "https://inference.coop",
-  "contactEmail": "info@inference.coop",
+  "contactEmail": "info@inference.coop"
-  "dockerImage": "registry.inference.coop/co-op/member-portal:20261102-5f8bed3"
 }