Implement autobackup-operator controllers, tests, CI and packaging

PVCs and CloudNativePG Clusters need S3 buckets and backup schedules
provisioned consistently. This operator watches the
backups.unkin.net/{schedule,destination} annotations on those objects and
provisions everything needed to back them up, with no new CRDs.

- Add a PVC controller that provisions cephrgw ObjectStoreUser/Bucket/BucketAccess,
  auto-generates a restic repo-password Secret and creates a k8up Schedule scoped
  to the PVC via spec.backup.volumes[].persistentVolumeClaim.claimName.
- Add a CNPG Cluster controller that provisions the same bucket stack, idempotently
  patches spec.backup.barmanObjectStore (leaving a user-set destinationPath alone
  with a Warning event) and creates a ScheduledBackup.
- Resolve destinations through a ConfigMap lookup table; requeue until the
  BucketAccess is Ready before creating schedule resources; own-reference created
  resources and retain bucket data by default.
- Add schedule-mapping helpers (k8up 5-field/shortcut pass-through, CNPG 6-field
  seconds-first) and deterministic, length-bounded name derivation.
- Add unit tests (schedule mapping, name derivation, destination resolution) and
  envtest controller tests for both paths, wiring the external CRDs into envtest.
- Add kubebuilder-generated RBAC, a Dockerfile (distroless/nonroot), Woodpecker
  lint/test/build pipelines and a tag-triggered image push to the artifactapi
  docker-internal registry, plus a version-bump Makefile and deploy manifests.

config/manager/manager.yaml

@@ -0,0 +1,64 @@
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: autobackup-operator
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: autobackup-operator
+  namespace: autobackup-operator
+  labels:
+    app: autobackup-operator
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app: autobackup-operator
+  template:
+    metadata:
+      labels:
+        app: autobackup-operator
+    spec:
+      serviceAccountName: autobackup-operator
+      securityContext:
+        runAsNonRoot: true
+      containers:
+        - name: operator
+          image: artifactapi.k8s.syd1.au.unkin.net/docker-internal/autobackup-operator:latest
+          args:
+            - --leader-elect
+          env:
+            - name: POD_NAMESPACE
+              valueFrom:
+                fieldRef:
+                  fieldPath: metadata.namespace
+          ports:
+            - name: metrics
+              containerPort: 8080
+            - name: probes
+              containerPort: 8081
+          livenessProbe:
+            httpGet:
+              path: /healthz
+              port: probes
+            initialDelaySeconds: 15
+            periodSeconds: 20
+          readinessProbe:
+            httpGet:
+              path: /readyz
+              port: probes
+            initialDelaySeconds: 5
+            periodSeconds: 10
+          securityContext:
+            allowPrivilegeEscalation: false
+            readOnlyRootFilesystem: true
+            capabilities:
+              drop: ["ALL"]
+          resources:
+            requests:
+              memory: 128Mi
+              cpu: 100m
+            limits:
+              memory: 512Mi
+              cpu: "1"