fix(admin): serialize replication metrics in minio-go wire shapes

?replication-metrics[=2] and the admin replicationmetrics endpoint
serialized the internal snake_case BucketStats family straight onto the
wire, so 'mc replicate status' decoded all zeros without any error
(backlog#1675 P1-11). The internal structs cannot be renamed: they are
the intra-cluster peer-RPC wire format (rmp_serde to_vec_named in
node_service.rs), pinned by a new regression test.

- New admin/replication_metrics_wire.rs: Serialize-only projections onto
  minio-go replication.Metrics (v1 body, currStats) and MetricsV2
  (uptime/currStats/queueStats/downtimeInfo) with the exact json tags;
  per-target failed becomes the TimedErrStats envelope fed from the
  FailStats rolling window; the queue peak is dual-emitted as max
  (MinIO server tag) and peak (minio-go tag).
- queueStats synthesizes one node from the bucket queue snapshot — the
  aggregation path leaves queue_stats.nodes empty, and mc treats an
  empty node list as 'no data' — and carries transfer summaries
  (Large/Small/Total) derived from the per-target xfer rates.
- Both endpoints share the DTOs; source-health extension keys
  (provider_available/cluster_complete/...) ride along and are ignored
  by Go decoders.
- Widen the ecstore replication_stats_boundary re-exports
  (BucketReplicationStat/InQueueMetric/XferStats) so the admin facade
  chain can name the projected types.

crates/ecstore/src/bucket/replication/replication_stats_boundary.rs

@@ -15,7 +15,9 @@
 #[cfg(test)]
 pub(crate) use rustfs_replication::FailStats;
 pub(crate) use rustfs_replication::{
-    ActiveWorkerStat, BucketReplicationStat, InQueueMetric, ProxyMetric, ProxyStatsCache, QueueCache, ReplicationMetricScope,
-    SRMetricsSummary, XferStats,
+    ActiveWorkerStat, ProxyMetric, ProxyStatsCache, QueueCache, ReplicationMetricScope, SRMetricsSummary,
 };
-pub use rustfs_replication::{BucketReplicationStats, BucketStats};
+// Public so the admin wire DTOs (rustfs/src/admin/replication_metrics_wire.rs)
+// can project the internal stats onto the minio-go response shapes through
+// the storage_api facade chain.
+pub use rustfs_replication::{BucketReplicationStat, BucketReplicationStats, BucketStats, InQueueMetric, XferStats};