fix(transport): stop scanning DataSourceReference for blocker references

DetectBlockersAsync was feeding TemplateAttribute.DataSourceReference
into the identifier scanner alongside script bodies, but that field is
an OPC UA node-address path (e.g. "ns=3;s=Tank.Level") owned by the
device, not script source. The dot delimiter inside the path tripped
the heuristic into flagging the address segment ("Tank", "Sensor",
"TestChildObject", "DevAppEngine") as a missing SharedScript or
ExternalSystem reference -- a 100% false-positive class on any
template catalog with OPC-UA-mapped attributes.

Drop the DataSourceReference scan entirely. Attribute.Value is still
scanned because it can carry a design-time default expression that
calls into runtime APIs. Add a regression test pinning the new behavior.

src/ScadaLink.Transport/Import/BundleImporter.cs

@@ -374,8 +374,13 @@ public sealed class BundleImporter : IBundleImporter
             foreach (var s in t.Scripts) CollectCallIdentifiers(s.Code, referencedFromBundle);
             foreach (var a in t.Attributes)
             {
+                // Attribute.Value carries the design-time default expression, which
+                // can be script-callable. DataSourceReference is an OPC UA node
+                // address path (e.g. "ns=3;s=Tank.Level") owned by the device --
+                // it's never script source and must NOT be scanned, or the dot
+                // delimiter trips the heuristic into flagging the address segments
+                // as missing SharedScript/ExternalSystem references.
                 CollectCallIdentifiers(a.Value, referencedFromBundle);
-                CollectCallIdentifiers(a.DataSourceReference, referencedFromBundle);
             }
         }
         foreach (var m in content.ApiMethods)