ci: add Gitea Actions workflow for build, push, and deploy

Self-hosted runner on haskelseed. Pipeline: nix build .#docker →
skopeo push to Gitea registry → helm upgrade on Railiance01 → smoke test.

Runner setup required (one-time):
  - Register Gitea Actions runner on haskelseed with label "haskelseed"
  - Set secrets: GITEA_TOKEN (package:write scope), RAILIANCE01_KUBECONFIG
  - helm + kubectl in runner PATH (or via nix)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/deploy.yaml

@@ -0,0 +1,60 @@
+name: Build and Deploy
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build-push-deploy:
+    runs-on: [self-hosted, haskelseed]
+    timeout-minutes: 120
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Build OCI image
+        shell: bash -l {0}
+        run: |
+          nix build .#docker \
+            --accept-flake-config \
+            --option lazy-trees false \
+            --log-format bar-with-logs
+
+      - name: Push image to Gitea registry
+        shell: bash -l {0}
+        env:
+          GITEA_TOKEN: ${{ secrets.GITEA_TOKEN }}
+        run: |
+          SHA=$(git rev-parse --short HEAD)
+          skopeo copy docker-archive:result \
+            "docker://92.205.130.254:32166/coulomb/inter-hub:${SHA}" \
+            --dest-creds "tegwick:${GITEA_TOKEN}" \
+            --dest-tls-verify=false
+          # Also tag as latest
+          skopeo copy docker-archive:result \
+            "docker://92.205.130.254:32166/coulomb/inter-hub:latest" \
+            --dest-creds "tegwick:${GITEA_TOKEN}" \
+            --dest-tls-verify=false
+          echo "Pushed inter-hub:${SHA} and inter-hub:latest"
+
+      - name: Deploy to Railiance01
+        shell: bash -l {0}
+        env:
+          KUBECONFIG: ${{ secrets.RAILIANCE01_KUBECONFIG }}
+        run: |
+          SHA=$(git rev-parse --short HEAD)
+          helm upgrade --install inter-hub deploy/helm/inter-hub \
+            --namespace inter-hub --create-namespace \
+            --set image.tag="${SHA}" \
+            --wait --timeout 5m
+
+      - name: Smoke test
+        run: |
+          # Give the new pod time to start
+          sleep 15
+          curl -sf --retry 5 --retry-delay 5 https://hub.coulomb.social/ \
+            | grep -q "Inter-Hub" && echo "Landing page OK"
+          curl -sf https://hub.coulomb.social/api/v2/hubs \
+            -o /dev/null -w "%{http_code}" | grep -q "401" && echo "API auth gate OK"