update DEV_PLAN with S3 remote storage and audit fixes

seaweed-volume/DEV_PLAN.md

@@ -4,7 +4,8 @@
 
 **HTTP tests**: 54/55 pass (98.2%) — 1 unfixable: CONNECT method is a hyper/axum limitation
 **gRPC tests**: 74/75 pass (98.7%) — 1 Go-only: TestVolumeMoveHandlesInFlightWrites uses Go binaries exclusively
-**Total**: 128/130 (98.5%)
+**S3 remote storage tests**: 3/3 pass (new)
+**Total**: 131/133 (98.5%) + 3 S3 tests
 **Rust unit tests**: 112 lib + 7 integration = 119
 
 ## Completed Features
@@ -18,32 +19,37 @@ All phases from the original plan are complete:
 - **Phase 2** — JWT/Security: signing keys from security.toml, token source precedence
   (query > header > cookie), file_id claims, leeway=0
 - **Phase 3** — gRPC: maintenance mode, error message parity, ping routing, batch delete,
-  VolumeServerStatus, ReadVolumeFileStatus
+  VolumeServerStatus (with real disk stats, data_center, rack), ReadVolumeFileStatus
+  (with timestamps)
 - **Phase 4** — Streaming gRPC: VolumeIncrementalCopy, CopyFile, ReceiveFile, ReadAllNeedles,
   VolumeTailSender, VolumeCopy, VolumeTailReceiver, VacuumVolumeCheck
 - **Phase 5** — EC Shards: mount/unmount, delete, read, blob delete, rebuild, shards-to-volume,
   copy, info
-- **Phase 6** — Advanced gRPC: ScrubVolume, ScrubEcVolume, Query, FetchAndWriteNeedle (stub),
+- **Phase 6** — Advanced gRPC: ScrubVolume, ScrubEcVolume, Query, FetchAndWriteNeedle,
   VolumeTierMoveDat (error paths)
+- **Phase 7** — Remote Storage: S3-compatible backend via aws-sdk-s3,
+  FetchAndWriteNeedle reads from S3/MinIO/SeaweedFS S3 and writes locally.
+  Supports all S3-compatible providers (AWS, Wasabi, Backblaze, Aliyun, etc.)
 - **Master Heartbeat** — Bidirectional streaming SendHeartbeat RPC, volume/EC registration,
   leader changes, shutdown deregistration. Tested end-to-end with Go master.
 
 ## Remaining Work (Production Readiness)
 
-All high-priority cluster operations are implemented (VacuumVolumeCompact/Commit/Cleanup,
-VolumeCopy, VolumeTailReceiver). Remaining items are lower priority:
-
 ### Medium Priority (nice to have)
 
-1. **Remote Storage** — `FetchAndWriteNeedle` with actual remote backend support.
-   Currently returns "remote storage not configured". Needed only if using tiered storage.
+1. **VolumeTierMoveDatToRemote/FromRemote** — Move volume data to/from remote storage
+   backends (S3, etc.). Currently returns error paths only. Would need to implement
+   full dat file upload/download to S3.
+
+2. **BatchDelete EC shards** — BatchDelete currently only handles regular volumes.
+   Go also checks EC volumes and calls DeleteEcShardNeedle.
 
-2. **VolumeTierMoveDatToRemote/FromRemote** — Move volume data to/from remote storage
-   backends (S3, etc.). Currently returns error paths only.
+3. **VolumeMarkReadonly persist flag** — Go persists readonly state to .vif file.
+   Rust only sets in-memory flag.
 
 ### Low Priority
 
-3. **TestUnsupportedMethodConnectParity** — HTTP CONNECT method returns 400 in Go but
+4. **TestUnsupportedMethodConnectParity** — HTTP CONNECT method returns 400 in Go but
    hyper rejects it before reaching the router. Would need a custom hyper service wrapper.
 
 ## Test Commands
@@ -55,6 +61,9 @@ cd seaweed-volume && cargo build --release
 # Run all Go integration tests with Rust volume server
 VOLUME_SERVER_IMPL=rust go test -v -count=1 -timeout 1200s ./test/volume_server/{grpc,http}/...
 
+# Run S3 remote storage tests
+VOLUME_SERVER_IMPL=rust go test -v -count=1 -timeout 180s -run "TestFetchAndWriteNeedle(FromS3|S3NotFound)" ./test/volume_server/grpc/...
+
 # Run specific test
 VOLUME_SERVER_IMPL=rust go test -v -count=1 -timeout 60s -run "TestName" ./test/volume_server/http/...