Scaffold kea-operator: CRDs, controllers, config rendering, REST API, CI

Replace the ISC dhcpd PXE-boot VM with a Kea DHCP Kubernetes operator, modelled
on bind-operator. The operator renders kea-dhcp4 config from CRs and runs an HA
pair of kea-dhcp4 + kea-ctrl-agent servers behind an anycast Service.

- add KeaCluster/KeaSubnet/KeaClientClass/KeaAPI CRDs (group kea.unkin.net)
- render deterministic kea-dhcp4.conf + kea-ctrl-agent.conf into a ConfigMap and
  roll the StatefulSet via a config-hash annotation; best-effort hot-reload via
  the kea-ctrl-agent REST channel
- run HA hot-standby (memfile leases) with stable per-peer DNS identity from a
  StatefulSet; expose an anycast LoadBalancer Service for PureLB
- represent the full legacy dhcpd config: 198.18.13-17.0/24 pools, pool-less
  198.18.25.0/24, and the Legacy/UEFI-64 PXE arch classes (option 93)
- add the KeaAPI-spawned REST service: Terraform-friendly CRUD over subnet and
  client-class CRs (stable IDs, PUT upsert, 404 drift, bearer-token auth)
- add Makefile (patch/minor/major tag targets), distroless operator/api images,
  an AlmaLinux+EPEL kea workload image, and woodpecker CI with k8s resources +
  serviceAccountName on every step
- unit tests for config rendering, controller reconcile/config-hash, and the API

Claude-Session: https://claude.ai/code/session_01JUoARVdmhxKQHyyyp1pxeT

config/samples/03-api.yaml

@@ -0,0 +1,21 @@
+# Optional: spawn the Terraform-friendly REST API that CRUDs KeaSubnet /
+# KeaClientClass CRs. Auth is a bearer token; the operator generates the token
+# Secret if absent, or it can be pre-seeded (e.g. by a Vault static secret).
+apiVersion: kea.unkin.net/v1alpha1
+kind: KeaAPI
+metadata:
+  name: kea-api
+  namespace: dhcp-system
+spec:
+  replicas: 1
+  image: git.unkin.net/unkin/kea-api:latest
+  service:
+    type: ClusterIP
+    port: 8080
+  resources:
+    requests:
+      cpu: 100m
+      memory: 64Mi
+    limits:
+      cpu: "1"
+      memory: 256Mi