deploy encapi to au-syd1 (#230)

## Why
encapi is the new Postgres-backed Puppet ENC that replaces Cobbler (Go API + encapi-cli + terraform provider). It needs to run somewhere reachable by the puppet masters (`encapi-cli classify`) and every node's `enc_direct_facts` fact. Deploy it in k8s alongside artifactapi, exposed at `encapi.k8s.syd1.au.unkin.net`.

## Changes
- add `apps/base/encapi/`: namespace, deployment (`git.unkin.net/unkin/encapi`, port 8000, `/healthz` probes), service, gateway + httproute (`encapi.k8s.syd1.au.unkin.net`, traefik-internal), configmap (DB coordinates), CNPG cluster + pooler (database `encapi`), and VaultAuth + VaultStaticSecrets (`postgres-credentials`, `environment`)
- add `apps/overlays/au-syd1/encapi` overlay referencing the base
- register `apps/overlays/*/encapi` in the platform ApplicationSet so ArgoCD picks it up

## Notes
- Mirrors the artifactapi pattern (VaultAuth role `default`, namespace-scoped VSO paths `kv/kubernetes/namespace/encapi/default/*`).
- Before first sync, seed the Vault KV secrets: `environment` must carry `DBPASS` (matching the CNPG owner password) and `ENCAPI_WRITE_TOKEN`; `postgres-credentials` carries the CNPG owner username/password.
- `kustomize build apps/overlays/au-syd1/encapi` validates clean (11 resources).

---------

Co-authored-by: unkinben <neotheo@gmail.com>
Reviewed-on: #230
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/base/encapi/deployment.yaml

@@ -0,0 +1,64 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: encapi
+  namespace: encapi
+  annotations:
+    reloader.stakater.com/auto: "true"
+spec:
+  replicas: 2
+  selector:
+    matchLabels:
+      app: encapi
+  strategy:
+    rollingUpdate:
+      maxUnavailable: 1
+    type: RollingUpdate
+  template:
+    metadata:
+      labels:
+        app: encapi
+    spec:
+      automountServiceAccountToken: true
+      containers:
+        - name: encapi
+          image: git.unkin.net/unkin/encapi:v0.1.1
+          imagePullPolicy: IfNotPresent
+          ports:
+            - containerPort: 8000
+              name: http
+              protocol: TCP
+          envFrom:
+            # DBHOST/DBNAME/DBPORT/DBUSER/DBSSL/LISTEN_ADDR
+            - configMapRef:
+                name: encapi-env
+                optional: false
+            # DBPASS + ENCAPI_WRITE_TOKEN (seeded in Vault, see cutover notes)
+            - secretRef:
+                name: environment
+                optional: false
+          livenessProbe:
+            httpGet:
+              path: /healthz
+              port: http
+            initialDelaySeconds: 15
+            periodSeconds: 30
+            timeoutSeconds: 5
+            failureThreshold: 3
+          readinessProbe:
+            httpGet:
+              path: /healthz
+              port: http
+            initialDelaySeconds: 5
+            periodSeconds: 5
+            timeoutSeconds: 5
+            failureThreshold: 3
+          resources:
+            requests:
+              cpu: 50m
+              memory: 64Mi
+            limits:
+              cpu: 500m
+              memory: 256Mi
+      restartPolicy: Always