feat: deploy to Frostmoln production (#3100)

Part of the dancefinder.unbound.se cutover to Frostmoln Production (infra: unboundsoftware/infra#1896, already applied).

- Replaces the AWS `deploy-prod` job (failing since CI left AWS) with `deploy-prod-frostmoln` (`deploy prod-frostmoln -n dancefinder`), as schemas did.
- Restricted securityContext (runAsNonRoot, drop ALL, seccomp RuntimeDefault) and `imagePullSecrets: oci-registry` (Platform registry).
- Switches to `nginxinc/nginx-unprivileged` (same pin as schemas-app), listening on 8080 as uid 101; the Service keeps port 80. Traefik Ingress for `/`, PDB, HPA moved to `-prod-frostmoln`; ALB Ingress dropped; Service ClusterIP.

Merging deploys to Frostmoln only; DNS still points at AWS until the cutover.

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

https://claude.ai/code/session_01H6eVuR4Yt3m7TbDTDwyZJi
Reviewed-on: https://gitea.unbound.se/dancefinder/dancefinder-app/pulls/3100

.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
-        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 dancefinder