feat: deploy to Frostmoln production (#1019)

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

- `deploy-prod` (AWS) has failed since CI left AWS (no `k8s.unbound.se` context on the runners). It's replaced by `deploy-prod-frostmoln`, as in unbound-site/lingonpaj-site: `deploy prod-frostmoln -n schemas` with the org's `FROSTMOLN_PRODUCTION_DEPLOY_KEY`, `FROSTMOLN_PRODUCTION_CLUSTER_ID` and `BUILDTOOLS_FROSTMOLN_PRODUCTION`.
- Restricted Pod Security: the image runs as `node` (uid 1000) with a matching securityContext. The service only writes under `/tmp` (cosmo composition).
- `secrets.yaml` (AWS ClusterSecretStore, RDS + CloudAMQP) → `secrets-prod-frostmoln.yaml`: the namespace's `frostmoln` SecretStore and the Frostmoln Secret `schemas` (`POSTGRES_URL`, `AMQP_URL`, `API_KEY`), written by infra's `seed-schemas.sh`. The file had no target suffix, so it applied to every target.
- `config-prod`/`pdb-prod` → `-prod-frostmoln`; the ALB ingress → a Traefik one for `/query` with a Let's Encrypt certificate.

Checked locally (amd64): runs as uid 1000 with all capabilities dropped, `wgc` works, `/tmp` writable; it fails only on the (dummy) database, as expected.

**Merge after** infra#1878 is applied and `seed-schemas.sh` + `migrate-schemas-db.sh` have run. `schemas.unbound.se` keeps pointing at AWS until the cut-over.

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

https://claude.ai/code/session_01Ma8eHhW59hLAJuLzBnLvUu
Reviewed-on: #1019

Dockerfile

@@ -42,4 +42,8 @@ COPY --from=build /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
 # Copy the service binary
 COPY --from=build /release/service /
 
+# The image's own non-root user: Frostmoln enforces restricted Pod Security.
+# The service only writes under /tmp (cosmo composition).
+USER node
+
 CMD ["/service"]