Point issue-core default backend at Forgejo after Gitea retirement

Legacy in-cluster gitea-http repos are archived (issue create 423). Route
the default ingestion backend to https://forgejo.coulomb.social with
the-custodian as the central automation task inbox.

k8s/railiance/configmap-backends.yaml

@@ -1,7 +1,8 @@
-# Non-secret backend structure for issue-core inside railiance01.
-# Default backend = cluster Gitea (markitect). The Gitea token is NOT here;
-# it is injected at startup from GITEA_BACKEND_TOKEN (ExternalSecret) where the
-# template carries the sentinel "__FROM_ENV__".
+# Non-secret backend structure for issue-core on CoulombCore.
+# Default backend = Forgejo task inbox (Gitea-compatible API). Legacy in-cluster
+# gitea-http was retired; all coulomb/* repos there are archived (issue create 423).
+# Token is injected at startup from GITEA_BACKEND_TOKEN (ExternalSecret) — must be
+# a Forgejo API token with issues:create on the default repo.
 apiVersion: v1
 kind: ConfigMap
 metadata:
@@ -13,12 +14,12 @@ metadata:
 data:
   backends.json: |
     {
-      "markitect": {
+      "forgejo-inbox": {
         "type": "gitea",
-        "base_url": "http://gitea-http.default.svc.cluster.local:3000",
+        "base_url": "https://forgejo.coulomb.social",
         "owner": "coulomb",
-        "repo": "markitect-main",
+        "repo": "the-custodian",
         "token": "__FROM_ENV__"
       },
-      "default": "markitect"
+      "default": "forgejo-inbox"
     }