ci(deploy): deploy the stack to Talos on merge to main (refs #175)

The chart has been deployable by hand since #25 and linted in CI since #168;
this makes a merged PR actually ship it to the lab server's Talos VM.

Neither the Kubernetes API nor the in-cluster registry is publicly reachable,
so the job forwards 6443, 30500 and 30141 over the same SSH hop into the Fedora
host that the Gitea-runner pipeline uses. That splits the registry into two
names for one store: images are pushed through the tunnel to localhost:30500,
and the node pulls them from its own NodePort — the address its registry-mirror
patch trusts over plain HTTP.

It deploys with `make k8s-reseed` rather than `make k8s-up`: the bootstrap Jobs
are idempotent, and deleting them first is what stops a changed Job template
from wedging `helm upgrade`. The nine deployments are then rolled explicitly,
because `dev` is a mutable tag and helm sees an unchanged pod template.

PR CI is the merge gate, so this workflow does not re-run the checks. Deploys
queue instead of cancelling: a `helm upgrade` killed half-way leaves the release
in `pending-upgrade` and needs unwedging by hand.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/runbooks/kubernetes-talos.md

@@ -360,6 +360,47 @@ immutable, so `helm upgrade` is rejected with `cannot patch "…" with kind Job`
 | Pods `Evicted` / `OOMKilled` | the VM is too small (§0) |
 | A Job shows `BackoffLimitExceeded` | read it: `kubectl -n big logs job/<name>` |
 
+## 9. Deploying on merge to main
+
+`.gitea/workflows/deploy.yaml` runs the §3–§4 steps against the **lab server's** Talos VM
+every time a PR is squash-merged to `main` (and on demand via *Run workflow*). PR CI is the
+merge gate, so the workflow deploys without re-running the checks.
+
+The cluster's API and registry are not exposed publicly, so the job forwards them over the
+same SSH hop the Gitea-runner pipeline uses:
+
+```
+ssh -p 6667 user@labs.respellion.tech  -L 6443 -L 30500 -L 30141  →  <TALOS_VM_IP>
+```
+
+Consequences worth knowing:
+
+- Images are **pushed** to `localhost:30500` (the tunnel) and **pulled** by the node from
+  `<TALOS_VM_IP>:30500` (its own NodePort, the address in the Talos registry-mirror patch).
+  Same registry, two names — hence the two `K8S_REGISTRY` values in the workflow.
+- It calls `make k8s-reseed`, not `make k8s-up`: the bootstrap Jobs are idempotent, and
+  deleting them first is what stops a changed Job template from wedging `helm upgrade` (§7).
+- `dev` is a mutable tag, so a `rollout restart` of the nine repo deployments is what
+  actually puts the new images in the pods.
+- Deploys **queue** (`cancel-in-progress: false`): a helm upgrade killed half-way leaves the
+  release in `pending-upgrade`, which has to be unwedged by hand.
+
+Settings, all on the repository in Gitea:
+
+| Kind | Name | What |
+|---|---|---|
+| Secret | `TALOS_SSH_KEY` | private key for `user@labs.respellion.tech` (the Fedora host) |
+| Secret | `TALOS_KUBECONFIG` | base64 of the kubeconfig, **`server: https://127.0.0.1:6443`** — Talos puts `127.0.0.1` in the apiserver cert SANs, so TLS still verifies through the tunnel |
+| Variable | `TALOS_VM_IP` | the VM's libvirt address (default `192.168.122.173`) |
+| Variable | `TALOS_HOST` | the browser-facing host baked into Keycloak's issuer (default `localhost`, see §5) |
+
+The last step smokes `GET /openbaar/register` through the openbaar portal, which exercises
+portal → Caddy → BFF → projection. An empty register passes; a 502 does not.
+
+Not covered: the portals still need `make k8s-portals` (or an SSH forward) to be usable in a
+browser, because PKCE needs a secure context (§5). Giving the server a hostname + TLS is the
+upgrade path.
+
 ## What is not ported
 
 - **Observability** (Tempo, Prometheus, Grafana) is defined but disabled — those are built