fix: Critical data loss bug in variant editor - removed overly aggressive column skip logic

Problem: Variant editor was skipping ALL columns with headers starting with 'Property '
(e.g., 'Property 1'), which caused complete data loss during serialization.

When users entered data but didn't rename the default column header, serializeToJSON()
would skip the column entirely, returning an empty array [] to the database.

Fix: Only skip columns with truly empty names, not default 'Property X' names.
Users can now save data even if they haven't renamed column headers.

Files changed:
- wwwroot/js/variant-editor.js: Removed propertyName.startsWith('Property ') check
- Areas/Admin/Views/VariantCollections/Create.cshtml: Updated cache-busting to v=20251113d
- Areas/Admin/Views/VariantCollections/Edit.cshtml: Updated cache-busting to v=20251113d

LittleShop/Areas/Admin/Views/VariantCollections/Create.cshtml

@@ -74,7 +74,7 @@
     <script src="~/lib/hammerjs/hammer.min.js?v=20251113c"></script>
 
     <!-- Variant Editor Module -->
-    <script src="~/js/variant-editor.js?v=20251113c"></script>
+    <script src="~/js/variant-editor.js?v=20251113d"></script>
 
     <!-- Initialize Variant Editor -->
     <script>

LittleShop/Areas/Admin/Views/VariantCollections/Edit.cshtml

@@ -85,7 +85,7 @@
     <script src="~/lib/hammerjs/hammer.min.js?v=20251113c"></script>
 
     <!-- Variant Editor Module -->
-    <script src="~/js/variant-editor.js?v=20251113c"></script>
+    <script src="~/js/variant-editor.js?v=20251113d"></script>
 
     <!-- Initialize Variant Editor -->
     <script>