fix(replication): carry failure rolling windows through cluster aggregation

Review: both metrics endpoints aggregate first, and FailStats::merge
dropped the process-local samples (which also never cross the peer-RPC
wire — serde-skipped), so lastMinute/lastHour serialized as zero right
after a failure while totals was nonzero.

- FailStats gains serializable last_minute/last_hour window snapshots
  (serde default: old nodes read zeros, new fields are ignored by old
  decoders), recomputed on every add_size and re-stamped at the
  per-node collection point (get_latest_replication_stats), and summed
  by merge.
- The wire DTO takes the component-wise max of the live samples and the
  snapshot, so both the single-node and the aggregated path report the
  window.
- Regression test drives a stat through rmp round trip + merge before
  serialization, as requested.

Also restore the #[allow(dead_code)] attribute to route_policy — the
new module declaration had been inserted between the attribute and its
item, which broke the -D warnings CI lanes.

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

@@ -704,6 +704,12 @@ impl ReplicationStats {
         } else {
             BucketReplicationStats::new()
         };
+        // Stamp the serializable failure windows from the live samples: the
+        // samples themselves do not cross the peer-RPC wire, so this snapshot
+        // is what cluster aggregation and the metrics endpoints see.
+        for stat in replication_stats.stats.values_mut() {
+            stat.fail_stats.refresh_windows();
+        }
         let uptime = if cache.contains_key(bucket) {
             SystemTime::now()
                 .duration_since(SystemTime::UNIX_EPOCH)