Add railiance01 deployment artifacts and fix container image build

Introduce Dockerfile, entrypoint, and k8s/railiance manifests for the
ArgoCD GitOps pilot (ISSUE-WP-0003). Rename the Gitea PyPI build arg to
GITEA_PYPI_INDEX_URL so pip still resolves dependencies from PyPI.

k8s/railiance/configmap-backends.yaml

@@ -0,0 +1,24 @@
+# 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__".
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: issue-core-backends
+  namespace: issue-core
+  labels:
+    app.kubernetes.io/name: issue-core
+    app.kubernetes.io/part-of: railiance-gitops
+data:
+  backends.json: |
+    {
+      "markitect": {
+        "type": "gitea",
+        "base_url": "http://gitea-http.default.svc.cluster.local:3000",
+        "owner": "coulomb",
+        "repo": "markitect_project",
+        "token": "__FROM_ENV__"
+      },
+      "default": "markitect"
+    }