feat: Implement variable product handling in OrderForm (Tokopedia pattern)

Following PROJECT_SOP.md section 5.7 - Variable Product Handling:

**Backend (OrdersController.php):**
- Updated /products/search endpoint to return:
  - Product type (simple/variable)
  - Variations array with attributes, prices, stock
  - Formatted attribute names (Color, Size, etc.)

**Frontend (OrderForm.tsx):**
- Updated ProductSearchItem type to include variations
- Updated LineItem type to support variation_id and variation_name
- Added variation selector drawer (mobile + desktop)
- Each variation = separate cart item row
- Display variation name below product name
- Fixed remove button to work with variations (by index)

**UX Pattern:**
1. Search product → If variable, show variation drawer
2. Select variation → Add as separate line item
3. Can add same product with different variations
4. Each variation shown clearly: 'Product Name' + 'Color: Red'

**Result:**
✅ Tokopedia/Shopee pattern implemented
✅ No auto-selection of first variation
✅ Each variation is independent cart item
✅ Works on mobile and desktop

**Next:** Fix PageHeader max-w-5xl to only apply on settings pages

includes/Api/OrdersController.php

@@ -1138,9 +1138,10 @@ class OrdersController {
 
     $prods = wc_get_products( $args );
     $rows  = array_map( function( $p ) {
-      return [
+      $data = [
         'id'           => $p->get_id(),
         'name'         => $p->get_name(),
+        'type'         => $p->get_type(),
         'price'        => (float) $p->get_price(),
         'regular_price' => (float) $p->get_regular_price(),
         'sale_price'   => $p->get_sale_price() ? (float) $p->get_sale_price() : null,
@@ -1148,7 +1149,41 @@ class OrdersController {
         'stock'        => $p->get_stock_quantity(),
         'virtual'      => $p->is_virtual(),
         'downloadable' => $p->is_downloadable(),
+        'variations'   => [],
       ];
+      
+      // If variable product, include variations
+      if ( $p->get_type() === 'variable' ) {
+        $variation_ids = $p->get_children();
+        foreach ( $variation_ids as $variation_id ) {
+          $variation = wc_get_product( $variation_id );
+          if ( ! $variation ) continue;
+          
+          // Get variation attributes
+          $attributes = [];
+          foreach ( $variation->get_variation_attributes() as $attr_name => $attr_value ) {
+            // Remove 'attribute_' prefix and format name
+            $clean_name = str_replace( 'attribute_', '', $attr_name );
+            $clean_name = str_replace( 'pa_', '', $clean_name ); // Remove taxonomy prefix if present
+            $clean_name = ucfirst( str_replace( [ '-', '_' ], ' ', $clean_name ) );
+            
+            $attributes[ $clean_name ] = $attr_value;
+          }
+          
+          $data['variations'][] = [
+            'id'         => $variation->get_id(),
+            'attributes' => $attributes,
+            'price'      => (float) $variation->get_price(),
+            'regular_price' => (float) $variation->get_regular_price(),
+            'sale_price' => $variation->get_sale_price() ? (float) $variation->get_sale_price() : null,
+            'sku'        => $variation->get_sku(),
+            'stock'      => $variation->get_stock_quantity(),
+            'in_stock'   => $variation->is_in_stock(),
+          ];
+        }
+      }
+      
+      return $data;
     }, $prods );
 
     return new WP_REST_Response( [ 'rows' => $rows ], 200 );