Initial cephrgw-operator: Ceph RGW buckets & keys via dashboard API

Adds a Kubernetes operator that provisions Ceph RGW (S3) buckets and
access keys declaratively through the Ceph manager dashboard REST API.

Three CRDs in group ceph.unkin.net/v1alpha1:
- ObjectStoreUser: creates an RGW user, delivers its key pair to a Secret
- Bucket: creates an S3 bucket owned by an ObjectStoreUser; owns the
  bucket's aggregate S3 policy (union of all BucketAccess grants)
- BucketAccess: grants read-only/read-write/full access, provisioning a
  dedicated user (or reusing a referenced one) and delivering RW/RO keys

The internal/ceph client wraps the dashboard /api/auth, /api/rgw/user and
/api/rgw/bucket endpoints with lazy token auth and re-auth on 401. Bucket
policies are rendered deterministically and applied via the bucket
policy API (Reef 18.2+). Credentials come from the cephrgw-credentials
Secret via env. Includes generated CRDs/RBAC, samples, kind manifests,
Woodpecker CI, and docs/ceph-setup.md covering the required Ceph
dashboard account, RGW wiring and permissions.

hack/kind/manifests/namespace.yaml

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+---
+apiVersion: v1
+kind: Namespace
+metadata:
+  name: cephrgw-system

hack/kind/manifests/operator-deployment.yaml

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+---
+# Dashboard credentials for local testing. Replace the values, or create the
+# Secret out-of-band, before applying. Keys map 1:1 to the operator env vars.
+apiVersion: v1
+kind: Secret
+metadata:
+  name: cephrgw-credentials
+  namespace: cephrgw-system
+type: Opaque
+stringData:
+  CEPH_DASHBOARD_URL: "https://dashboard.ceph.unkin.net"
+  CEPH_DASHBOARD_USERNAME: "k8s-cephrgw-operator"
+  CEPH_DASHBOARD_PASSWORD: "change-me"
+  # Optional: the S3 endpoint written into credential Secrets for consumers.
+  CEPH_RGW_ENDPOINT: "https://s3.ceph.unkin.net"
+  # Optional: set to "true" to skip TLS verification (dev only).
+  # CEPH_DASHBOARD_INSECURE: "true"
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: cephrgw-operator
+  namespace: cephrgw-system
+  labels:
+    app.kubernetes.io/name: cephrgw-operator
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: cephrgw-operator
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: cephrgw-operator
+    spec:
+      serviceAccountName: cephrgw-operator
+      securityContext:
+        runAsNonRoot: true
+      containers:
+        - name: operator
+          image: cephrgw-operator:dev
+          imagePullPolicy: IfNotPresent
+          args:
+            - --metrics-bind-address=:8080
+            - --health-probe-bind-address=:8081
+            - --leader-elect
+          envFrom:
+            - secretRef:
+                name: cephrgw-credentials
+          ports:
+            - containerPort: 8080
+              name: metrics
+            - containerPort: 8081
+              name: health
+          readinessProbe:
+            httpGet:
+              path: /readyz
+              port: 8081
+          livenessProbe:
+            httpGet:
+              path: /healthz
+              port: 8081
+          securityContext:
+            allowPrivilegeEscalation: false
+            readOnlyRootFilesystem: true
+            capabilities:
+              drop: ["ALL"]
+          resources:
+            requests:
+              cpu: 50m
+              memory: 64Mi
+            limits:
+              cpu: 500m
+              memory: 256Mi

hack/kind/manifests/rbac.yaml

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+---
+apiVersion: v1
+kind: ServiceAccount
+metadata:
+  name: cephrgw-operator
+  namespace: cephrgw-system
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRole
+metadata:
+  name: cephrgw-operator
+rules:
+  - apiGroups: ["ceph.unkin.net"]
+    resources: ["*"]
+    verbs: ["*"]
+  - apiGroups: [""]
+    resources: ["secrets"]
+    verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
+  - apiGroups: [""]
+    resources: ["events"]
+    verbs: ["create", "patch"]
+  - apiGroups: ["coordination.k8s.io"]
+    resources: ["leases"]
+    verbs: ["get", "list", "watch", "create", "update", "patch", "delete"]
+---
+apiVersion: rbac.authorization.k8s.io/v1
+kind: ClusterRoleBinding
+metadata:
+  name: cephrgw-operator
+subjects:
+  - kind: ServiceAccount
+    name: cephrgw-operator
+    namespace: cephrgw-system
+roleRef:
+  apiGroup: rbac.authorization.k8s.io
+  kind: ClusterRole
+  name: cephrgw-operator