fix: Mobile accordion + deduplicate shipping methods

Fixes:
✅ Issue #2: Mobile drawer now uses accordion (no nested modals)
✅ Issue #3: Duplicate "Local pickup" - now shows as:
   - Local pickup
   - Local pickup (local_pickup_plus)

Changes:
- Mobile drawer matches desktop accordion pattern
- Smaller text/spacing for mobile
- Deduplication logic in backend API
- Adds method ID suffix for duplicate titles

Result:
✅ No modal-over-modal on any device
✅ Consistent UX desktop/mobile
✅ Clear distinction between similar methods

includes/Api/ShippingController.php

@@ -398,10 +398,21 @@ class ShippingController extends WP_REST_Controller {
 			$methods = $shipping->get_shipping_methods();
 			
 			$available = array();
+			$seen_titles = array();
+			
 			foreach ( $methods as $method ) {
+				$title = $method->get_method_title();
+				$id = $method->id;
+				
+				// Deduplicate by adding ID suffix if title already exists
+				if ( isset( $seen_titles[ $title ] ) ) {
+					$title .= ' (' . $id . ')';
+				}
+				$seen_titles[ $title ] = true;
+				
 				$available[] = array(
-					'id'          => $method->id,
-					'title'       => $method->get_method_title(),
+					'id'          => $id,
+					'title'       => $title,
 					'description' => $method->get_method_description(),
 				);
 			}