Talk to radosgw directly via go-ceph + aws-sdk-go-v2

The operator drove the Ceph manager dashboard REST API to manage RGW users,
buckets and policies. That coupled it to a dashboard login, the dashboard's RGW
wiring, and the dashboard's bucket API surface. Rebuild the Ceph integration to
talk directly to radosgw the way the CLI does, using native Go libraries, while
keeping every operator capability identical.

The exported surface of internal/ceph is unchanged, so the three controllers
and cmd/operator's structure are untouched (bar the CEPH_RGW_* config plumbing).

- replace the internal/ceph client internals with github.com/ceph/go-ceph
  rgw/admin (Admin Ops API) for users, keys, quotas and bucket info/removal
- add github.com/aws/aws-sdk-go-v2 S3 client for bucket create, versioning,
  policy, tagging and object lock, signed as the bucket owner
- map go-ceph admin.ErrNoSuch*/ErrUserExists and smithy APIError codes into
  IsNotFound/IsConflict so controller create-vs-update branching is preserved
- set S3 path-style addressing and WhenRequired checksum modes for RGW
- delete the hand-rolled dashboard client, token auth and JSON plumbing
- keep policy.go/BuildBucketPolicy/BuildTagJSON as pure builders
- replace the client tests with NewClient validation and error-classifier tests
- keep CGO_ENABLED=0 distroless: only go-ceph's pure-Go rgw/admin is imported
- switch env/config to CEPH_RGW_* (endpoint, admin endpoint, access/secret key,
  region, CA, insecure) and update the deployment manifest
- rewrite README and docs/ceph-setup.md for the single RGW admin user
  (caps users=*;buckets=*), keeping Vault/VSO as the primary credential source

Claude-Session: https://claude.ai/code/session_016CEncETbf8cvy1PhsHfFHM

go.mod

@@ -1,8 +1,13 @@
 module git.unkin.net/unkin/cephrgw-operator
 
-go 1.25
+go 1.25.0
 
 require (
+	github.com/aws/aws-sdk-go-v2 v1.43.0
+	github.com/aws/aws-sdk-go-v2/credentials v1.19.30
+	github.com/aws/aws-sdk-go-v2/service/s3 v1.106.0
+	github.com/aws/smithy-go v1.27.4
+	github.com/ceph/go-ceph v0.40.0
 	k8s.io/api v0.34.4
 	k8s.io/apimachinery v0.34.4
 	k8s.io/client-go v0.34.4
@@ -10,6 +15,14 @@ require (
 )
 
 require (
+	github.com/aws/aws-sdk-go-v2/aws/protocol/eventstream v1.7.14 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/configsources v1.4.31 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/endpoints/v2 v2.7.31 // indirect
+	github.com/aws/aws-sdk-go-v2/internal/v4a v1.4.32 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/accept-encoding v1.13.13 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/checksum v1.9.24 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/presigned-url v1.13.31 // indirect
+	github.com/aws/aws-sdk-go-v2/service/internal/s3shared v1.19.32 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
 	github.com/davecgh/go-spew v1.1.1 // indirect
@@ -48,7 +61,7 @@ require (
 	golang.org/x/net v0.38.0 // indirect
 	golang.org/x/oauth2 v0.27.0 // indirect
 	golang.org/x/sync v0.12.0 // indirect
-	golang.org/x/sys v0.31.0 // indirect
+	golang.org/x/sys v0.45.0 // indirect
 	golang.org/x/term v0.30.0 // indirect
 	golang.org/x/text v0.23.0 // indirect
 	golang.org/x/time v0.9.0 // indirect