feat(config): make Equipment.DriverInstanceId nullable + driver-less AdminUI support + migration

src/Core/ZB.MOM.WW.OtOpcUa.Configuration/Entities/Equipment.cs

@@ -19,8 +19,11 @@ public sealed class Equipment
     /// <summary>UUIDv4, IMMUTABLE across all generations of the same EquipmentId. Downstream-consumer join key.</summary>
     public Guid EquipmentUuid { get; set; }
 
-    /// <summary>Logical FK to the driver providing data for this equipment.</summary>
-    public required string DriverInstanceId { get; set; }
+    /// <summary>
+    ///     Optional logical FK to the driver providing data for this equipment.
+    ///     <c>null</c> = VirtualTag-only / driver-less equipment (no field driver).
+    /// </summary>
+    public string? DriverInstanceId { get; set; }
 
     /// <summary>Optional logical FK to a multi-device driver's device.</summary>
     public string? DeviceId { get; set; }