feat: deploy to Frostmoln production (#243)

Moves the production deploy from AWS to the Frostmoln production cluster (namespace `sites`).

- `deploy-prod` (AWS) has failed since CI left AWS: the runners have no `k8s.unbound.se` context, so the site on AWS still runs an older image. It's replaced by `deploy-prod-frostmoln`, the same pattern as Shiny's `deploy-frostmoln-staging`: `FROSTMOLN_PRODUCTION_DEPLOY_KEY` + `FROSTMOLN_PRODUCTION_CLUSTER_ID` (org), `BUILDTOOLS_FROSTMOLN_PRODUCTION` (org, target `prod-frostmoln`), `deploy prod-frostmoln -n sites`.
- Frostmoln enforces restricted Pod Security: the served image is `nginxinc/nginx-unprivileged` (uid 101, port 8080), with a matching securityContext; the Service is ClusterIP.
- `ingress-prod.yaml` (ALB) → `ingress-prod-frostmoln.yaml` (Traefik, Let's Encrypt).

Checked locally: the image serves `/health` and `/` (200) as uid 101 with all capabilities dropped.

**Merge after** infra's `feat/frostmoln-production-sites` is applied (namespace + org secret). The hostnames keep pointing at AWS until the Route 53 switch, a separate step; the certificate is issued after that.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

https://claude.ai/code/session_01Ma8eHhW59hLAJuLzBnLvUu
Reviewed-on: #243

.gitea/workflows/ci.yaml

@@ -18,16 +18,30 @@ jobs:
       - name: Build and push
         run: unset GITEA_TOKEN && build && push
 
-  deploy-prod:
+  deploy-prod-frostmoln:
     needs: build
     if: gitea.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
     env:
-      BUILDTOOLS_CONTENT: ${{ secrets.BUILDTOOLS_CONTENT }}
+      BUILDTOOLS_CONTENT: ${{ secrets.BUILDTOOLS_FROSTMOLN_PRODUCTION }}
       GITEA_REPOSITORY: ${{ gitea.repository }}
+      FM_TENANT: 9ae61342-0f76-476f-8176-e46f6b0b0c32
     environment: prod
     steps:
       - uses: actions/checkout@v7
       - uses: buildtool/setup-buildtools-action@v1
-      - name: Deploy to production
-        run: deploy prod
+      - name: Install fm
+        run: |
+          sudo install -d -m 0755 /etc/apt/keyrings
+          sudo curl -fsSL -o /etc/apt/keyrings/frostmoln.gpg https://get.frostmoln.cloud/deb/frostmoln.gpg
+          sudo curl -fsSL -o /etc/apt/sources.list.d/frostmoln.sources https://get.frostmoln.cloud/deb/frostmoln.sources
+          sudo apt-get update && sudo apt-get install -y fm
+      - name: Deploy to Frostmoln production
+        env:
+          FROSTMOLN_API_KEY: ${{ secrets.FROSTMOLN_PRODUCTION_DEPLOY_KEY }}
+        # The cluster API is private: the kubeconfig's exec plugin opens an fm
+        # tunnel on demand. fm reads the key from its config file, not the env.
+        run: |
+          fm auth api-key set "$FROSTMOLN_API_KEY" > /dev/null
+          fm kubernetes cluster kubeconfig ${{ vars.FROSTMOLN_PRODUCTION_CLUSTER_ID }} --exec --file "$RUNNER_TEMP/kubeconfig"
+          KUBECONFIG_CONTENT="$(cat "$RUNNER_TEMP/kubeconfig")" deploy prod-frostmoln -n sites