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/wwwroot/js/variant-editor.js

@@ -395,9 +395,9 @@ class VariantEditor {
         for (let col = 0; col < headers.length; col++) {
             const propertyName = headers[col];
 
-            // Skip empty column names or default column names
-            if (!propertyName || propertyName.trim() === '' || propertyName.startsWith('Property ')) {
-                console.log('Skipping column:', { colIndex: col, name: propertyName, reason: 'empty or default' });
+            // Skip only truly empty column names
+            if (!propertyName || propertyName.trim() === '') {
+                console.log('Skipping column:', { colIndex: col, name: propertyName, reason: 'empty name' });
                 continue;
             }