fix(config): DraftSnapshotFactory loads only active (unreleased) reservations

Filter ExternalIdReservations to WHERE ReleasedAt IS NULL so
DraftSnapshot.ActiveReservations matches its documented semantics and
ValidateReservationPreflight cannot emit spurious BadDuplicateExternalIdentifier
errors from already-released rows. Adds a focused unit test seeding one active
and one released reservation and asserting only the active row is returned.

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Validation/DraftSnapshotFactory.cs

@@ -43,6 +43,9 @@ public static class DraftSnapshotFactory
             VirtualTags        = await db.VirtualTags.AsNoTracking().ToListAsync(ct),
             PollGroups         = await db.PollGroups.AsNoTracking().ToListAsync(ct),
             PriorEquipment     = [],
-            ActiveReservations = await db.ExternalIdReservations.AsNoTracking().ToListAsync(ct),
+            ActiveReservations = await db.ExternalIdReservations
+                .AsNoTracking()
+                .Where(r => r.ReleasedAt == null)   // active only — matches DraftSnapshot.ActiveReservations semantics
+                .ToListAsync(ct),
         };
 }

tests/Core/ZB.MOM.WW.OtOpcUa.Configuration.Tests/DraftSnapshotFactoryTests.cs

@@ -63,6 +63,44 @@ public sealed class DraftSnapshotFactoryTests : IDisposable
         DraftValidator.Validate(snapshot).ShouldNotContain(e => e.Code == "EquipmentSignalNameCollision");
     }
 
+    /// <summary>Seeds one active and one released reservation for the same equipment context;
+    /// only the active row (ReleasedAt == null) should appear in the snapshot.</summary>
+    [Fact]
+    public async Task FromConfigDb_ActiveReservations_excludes_released_rows()
+    {
+        var equipmentUuid = Guid.NewGuid();
+
+        _db.ExternalIdReservations.Add(new ExternalIdReservation
+        {
+            ReservationId    = Guid.NewGuid(),
+            Kind             = ReservationKind.ZTag,
+            Value            = "ZT-001",
+            EquipmentUuid    = equipmentUuid,
+            ClusterId        = "cluster-a",
+            FirstPublishedBy = "test",
+            ReleasedAt       = null,         // active
+        });
+        _db.ExternalIdReservations.Add(new ExternalIdReservation
+        {
+            ReservationId    = Guid.NewGuid(),
+            Kind             = ReservationKind.ZTag,
+            Value            = "ZT-002",
+            EquipmentUuid    = equipmentUuid,
+            ClusterId        = "cluster-a",
+            FirstPublishedBy = "test",
+            ReleasedAt       = new DateTime(2025, 1, 1, 0, 0, 0, DateTimeKind.Utc),  // released
+            ReleasedBy       = "test",
+            ReleaseReason    = "retired",
+        });
+        await _db.SaveChangesAsync();
+
+        var snapshot = await DraftSnapshotFactory.FromConfigDbAsync(_db);
+
+        snapshot.ActiveReservations.Count.ShouldBe(1);
+        snapshot.ActiveReservations[0].Value.ShouldBe("ZT-001");
+        snapshot.ActiveReservations[0].ReleasedAt.ShouldBeNull();
+    }
+
     private void SeedEquipment(string equipmentId)
     {
         var uuid = Guid.NewGuid();