feat(management): secured-write list paging with TotalCount (arch-review P3)

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.ManagementService/ManagementActor.cs

@@ -1394,7 +1394,13 @@ public class ManagementActor : ReceiveActor
         IServiceProvider sp, ListSecuredWritesCommand cmd)
     {
         var repo = sp.GetRequiredService<ISecuredWriteRepository>();
-        var rows = await repo.QueryAsync(cmd.Status, cmd.SiteId, skip: 0, take: 200);
+
+        // Offset paging (arch-review P3): clamp untrusted paging inputs so a crafted
+        // command can neither request a negative offset nor an unbounded page.
+        var take = Math.Clamp(cmd.Take, 1, 500);
+        var skip = Math.Max(0, cmd.Skip);
+        var rows = await repo.QueryAsync(cmd.Status, cmd.SiteId, skip, take);
+        var totalCount = await repo.CountAsync(cmd.Status, cmd.SiteId);
 
         // Opportunistic expiry sweep (arch-review S2): every time the list is read, walk
         // the page and expire any overdue Pending row. TryExpireIfStaleAsync self-filters
@@ -1411,7 +1417,7 @@ public class ManagementActor : ReceiveActor
                 await TryExpireIfStaleAsync(sp, repo, row);
         }
 
-        return new SecuredWriteListResult(rows.Select(ToSecuredWriteDto).ToList());
+        return new SecuredWriteListResult(rows.Select(ToSecuredWriteDto).ToList(), totalCount);
     }
 
     // ========================================================================