feat(checkout): implement dynamic shipping rate fetching

Backend:
- Added /checkout/shipping-rates REST endpoint
- Returns available shipping methods from matching zone
- Triggers woonoow/shipping/before_calculate hook for Rajaongkir

Frontend:
- Added ShippingRate interface and state
- Added fetchShippingRates with 500ms debounce
- Replaced hardcoded shipping options with dynamic rates
- Added loading and empty state handling
- Added shipping_method to order submission payload

This fixes:
- Rajaongkir rates not appearing (now fetched from API)
- Free shipping showing despite disabled (now from WC zones)

includes/Api/CheckoutController.php

@@ -50,6 +50,12 @@ class CheckoutController {
                 ],
             ],
         ]);
+        // Get available shipping rates for given address
+        register_rest_route($namespace, '/checkout/shipping-rates', [
+            'methods'  => 'POST',
+            'callback' => [ new self(), 'get_shipping_rates' ],
+            'permission_callback' => [ \WooNooW\Api\Permissions::class, 'anon_or_wp_nonce' ],
+        ]);
     }
 
     /**
@@ -773,4 +779,123 @@ class CheckoutController {
             'default_country' => $default_country,
         ];
     }
+
+    /**
+     * Get available shipping rates for given address
+     * POST /checkout/shipping-rates
+     * Body: { shipping: { country, state, city, postcode, destination_id? }, items: [...] }
+     */
+    public function get_shipping_rates(WP_REST_Request $r): array {
+        $payload = $r->get_json_params();
+        $shipping = $payload['shipping'] ?? [];
+        $items = $payload['items'] ?? [];
+        
+        $country = wc_clean($shipping['country'] ?? '');
+        $state = wc_clean($shipping['state'] ?? '');
+        $city = wc_clean($shipping['city'] ?? '');
+        $postcode = wc_clean($shipping['postcode'] ?? '');
+        
+        if (empty($country)) {
+            return [
+                'ok' => true,
+                'rates' => [],
+                'message' => 'Country is required',
+            ];
+        }
+        
+        // Trigger hook for plugins to set session data (e.g., Rajaongkir destination_id)
+        do_action('woonoow/shipping/before_calculate', $shipping, $items);
+        
+        // Set customer location for shipping calculation
+        if (WC()->customer) {
+            WC()->customer->set_shipping_country($country);
+            WC()->customer->set_shipping_state($state);
+            WC()->customer->set_shipping_city($city);
+            WC()->customer->set_shipping_postcode($postcode);
+        }
+        
+        // Build package for shipping calculation
+        $contents = [];
+        $contents_cost = 0;
+        foreach ($items as $item) {
+            $product = wc_get_product($item['product_id'] ?? 0);
+            if (!$product) continue;
+            $qty = max(1, (int)($item['quantity'] ?? $item['qty'] ?? 1));
+            $price = (float) wc_get_price_to_display($product);
+            $contents[] = [
+                'data' => $product,
+                'quantity' => $qty,
+                'line_total' => $price * $qty,
+            ];
+            $contents_cost += $price * $qty;
+        }
+        
+        $package = [
+            'destination' => [
+                'country' => $country,
+                'state' => $state,
+                'city' => $city,
+                'postcode' => $postcode,
+            ],
+            'contents' => $contents,
+            'contents_cost' => $contents_cost,
+            'applied_coupons' => [],
+            'user' => ['ID' => get_current_user_id()],
+        ];
+        
+        // Get matching shipping zone
+        $zone = WC_Shipping_Zones::get_zone_matching_package($package);
+        if (!$zone) {
+            return [
+                'ok' => true,
+                'rates' => [],
+                'message' => 'No shipping zone matches your location',
+            ];
+        }
+        
+        // Get enabled shipping methods from zone
+        $methods = $zone->get_shipping_methods(true);
+        $rates = [];
+        
+        foreach ($methods as $method) {
+            // Check if method has rates (some methods like live rate need to calculate)
+            if (method_exists($method, 'get_rates_for_package')) {
+                $method_rates = $method->get_rates_for_package($package);
+                foreach ($method_rates as $rate) {
+                    $rates[] = [
+                        'id' => $rate->get_id(),
+                        'label' => $rate->get_label(),
+                        'cost' => (float) $rate->get_cost(),
+                        'method_id' => $rate->get_method_id(),
+                        'instance_id' => $rate->get_instance_id(),
+                    ];
+                }
+            } else {
+                // Fallback for simple methods
+                $method_id = $method->id . ':' . $method->get_instance_id();
+                $cost = 0;
+                
+                // Try to get cost from method
+                if (isset($method->cost)) {
+                    $cost = (float) $method->cost;
+                } elseif (method_exists($method, 'get_option')) {
+                    $cost = (float) $method->get_option('cost', 0);
+                }
+                
+                $rates[] = [
+                    'id' => $method_id,
+                    'label' => $method->get_title(),
+                    'cost' => $cost,
+                    'method_id' => $method->id,
+                    'instance_id' => $method->get_instance_id(),
+                ];
+            }
+        }
+        
+        return [
+            'ok' => true,
+            'rates' => $rates,
+            'zone_name' => $zone->get_zone_name(),
+        ];
+    }
 }