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.

internal/controller/schedule.go

@@ -0,0 +1,99 @@
+package controller
+
+import (
+	"fmt"
+	"strings"
+)
+
+// cnpgShortcuts expands cron nickname shortcuts to the 6-field (seconds-first)
+// cron expressions CloudNativePG's robfig/cron parser expects.
+var cnpgShortcuts = map[string]string{
+	"@hourly":   "0 0 * * * *",
+	"@daily":    "0 0 0 * * *",
+	"@midnight": "0 0 0 * * *",
+	"@weekly":   "0 0 0 * * 0",
+	"@monthly":  "0 0 0 1 * *",
+	"@yearly":   "0 0 0 1 1 *",
+	"@annually": "0 0 0 1 1 *",
+}
+
+// k8upShortcuts is the set of cron nicknames k8up accepts natively (passed
+// through unchanged).
+var k8upShortcuts = map[string]bool{
+	"@hourly": true, "@daily": true, "@midnight": true, "@weekly": true,
+	"@monthly": true, "@yearly": true, "@annually": true,
+}
+
+// ScheduleForK8up validates a schedule annotation for k8up, which accepts cron
+// nickname shortcuts natively and otherwise expects a 5-field cron expression.
+// A valid value is returned unchanged.
+func ScheduleForK8up(in string) (string, error) {
+	s := strings.TrimSpace(in)
+	if s == "" {
+		return "", fmt.Errorf("empty schedule")
+	}
+	if strings.HasPrefix(s, "@") {
+		if k8upShortcuts[s] {
+			return s, nil
+		}
+		return "", fmt.Errorf("unsupported schedule shortcut %q", s)
+	}
+	if err := validateCronFields(s, 5); err != nil {
+		return "", err
+	}
+	return s, nil
+}
+
+// ScheduleForCNPG normalises a schedule annotation into the 6-field
+// (seconds-first) cron format a CloudNativePG ScheduledBackup requires:
+// shortcuts expand to explicit expressions, a 5-field cron gains a leading "0"
+// seconds field, and a 6-field cron is accepted as-is.
+func ScheduleForCNPG(in string) (string, error) {
+	s := strings.TrimSpace(in)
+	if s == "" {
+		return "", fmt.Errorf("empty schedule")
+	}
+	if strings.HasPrefix(s, "@") {
+		if v, ok := cnpgShortcuts[s]; ok {
+			return v, nil
+		}
+		return "", fmt.Errorf("unsupported schedule shortcut %q", s)
+	}
+	fields := strings.Fields(s)
+	switch len(fields) {
+	case 5:
+		if err := validateCronFields(s, 5); err != nil {
+			return "", err
+		}
+		return "0 " + strings.Join(fields, " "), nil
+	case 6:
+		if err := validateCronFields(s, 6); err != nil {
+			return "", err
+		}
+		return strings.Join(fields, " "), nil
+	default:
+		return "", fmt.Errorf("cron %q must have 5 or 6 fields, got %d", s, len(fields))
+	}
+}
+
+func validateCronFields(s string, want int) error {
+	fields := strings.Fields(s)
+	if len(fields) != want {
+		return fmt.Errorf("cron %q must have %d fields, got %d", s, want, len(fields))
+	}
+	for _, f := range fields {
+		if f == "" {
+			return fmt.Errorf("cron %q has an empty field", s)
+		}
+		for _, r := range f {
+			if !isCronRune(r) {
+				return fmt.Errorf("cron field %q contains invalid character %q", f, string(r))
+			}
+		}
+	}
+	return nil
+}
+
+func isCronRune(r rune) bool {
+	return (r >= '0' && r <= '9') || r == '*' || r == '/' || r == ',' || r == '-' || r == '?'
+}