feat: Add variation-level license duration to product editor

- Added license_duration_days field to ProductVariant type
- Added License Duration input to each variation card
- Backend: ProductsController saves/loads variation-level _license_duration_days meta
- Allows different license periods per variation (e.g., 1-year, 2-year, lifetime)

admin-spa/src/routes/Products/partials/tabs/VariationsTab.tsx

@@ -22,6 +22,7 @@ export type ProductVariant = {
   manage_stock?: boolean;
   stock_status?: 'instock' | 'outofstock' | 'onbackorder';
   image?: string;
+  license_duration_days?: string;
 };
 
 type VariationsTabProps = {
@@ -276,6 +277,26 @@ export function VariationsTab({
                         )}
                       </div>
                     </div>
+
+                    {/* License Duration - only show if licensing is enabled on product */}
+                    <div className="col-span-2 md:col-span-4">
+                      <Label className="text-xs">{__('License Duration (Days)')}</Label>
+                      <Input
+                        type="number"
+                        min="0"
+                        placeholder={__('Leave empty to use product default')}
+                        value={variation.license_duration_days || ''}
+                        onChange={(e) => {
+                          const updated = [...variations];
+                          updated[index].license_duration_days = e.target.value;
+                          setVariations(updated);
+                        }}
+                        className="mt-1"
+                      />
+                      <p className="text-xs text-muted-foreground mt-1">
+                        {__('Override license duration for this variation. 0 = never expires.')}
+                      </p>
+                    </div>
                     <div className="grid grid-cols-2 md:grid-cols-4 gap-3">
                       <Input
                         placeholder={__('SKU')}

includes/Api/ProductsController.php

@@ -898,6 +898,7 @@ class ProductsController {
 					'image_id' => $variation->get_image_id(),
 					'image_url' => $image_url,
 					'image' => $image_url, // For form compatibility
+					'license_duration_days' => get_post_meta($variation->get_id(), '_license_duration_days', true) ?: '',
 				];
 			}
 		}
@@ -994,6 +995,11 @@ class ProductsController {
 			$saved_id = $variation->save();
 			$variations_to_keep[] = $saved_id;
 			
+			// Save variation-level license duration
+			if (isset($var_data['license_duration_days'])) {
+				update_post_meta($saved_id, '_license_duration_days', self::sanitize_number($var_data['license_duration_days']));
+			}
+			
 			// Manually save attributes using direct database insert
 			if (!empty($wc_attributes)) {
 				global $wpdb;