feat: Newsletter system improvements and validation framework

- Fix: Marketing events now display in Staff notifications tab
- Reorganize: Move Coupons to Marketing/Coupons for better organization
- Add: Comprehensive email/phone validation with extensible filter hooks
  - Email validation with regex pattern (xxxx@xxxx.xx)
  - Phone validation with WhatsApp verification support
  - Filter hooks for external API integration (QuickEmailVerification, etc.)
- Fix: Newsletter template routes now use centralized notification email builder
- Add: Validation.php class for reusable validation logic
- Add: VALIDATION_HOOKS.md documentation with integration examples
- Add: NEWSLETTER_CAMPAIGN_PLAN.md architecture for future campaign system
- Fix: API delete method call in Newsletter.tsx (delete -> del)
- Remove: Duplicate EmailTemplates.tsx (using notification system instead)
- Update: Newsletter controller to use centralized Validation class

Breaking changes:
- Coupons routes moved from /routes/Coupons to /routes/Marketing/Coupons
- Legacy /coupons routes maintained for backward compatibility

includes/Api/NewsletterController.php

@@ -4,6 +4,7 @@ namespace WooNooW\API;
 use WP_REST_Request;
 use WP_REST_Response;
 use WP_Error;
+use WooNooW\Core\Validation;
 
 class NewsletterController {
     const API_NAMESPACE = 'woonoow/v1';
@@ -112,8 +113,11 @@ class NewsletterController {
     public static function subscribe(WP_REST_Request $request) {
         $email = sanitize_email($request->get_param('email'));
         
-        if (!is_email($email)) {
-            return new WP_Error('invalid_email', 'Invalid email address', ['status' => 400]);
+        // Use centralized validation with extensible filter hooks
+        $validation = Validation::validate_email($email, 'newsletter_subscribe');
+        
+        if (is_wp_error($validation)) {
+            return $validation;
         }
         
         // Get existing subscribers (now stored as objects with metadata)

includes/Api/ProductsController.php

@@ -68,19 +68,12 @@ class ProductsController {
 	 * Register REST API routes
 	 */
 	public static function register_routes() {
-		error_log('WooNooW ProductsController::register_routes() START');
-		
 		// List products
-		$callback = [__CLASS__, 'get_products'];
-		$is_callable = is_callable($callback);
-		error_log('WooNooW ProductsController: Callback is_callable: ' . ($is_callable ? 'YES' : 'NO'));
-		
-		$result = register_rest_route('woonoow/v1', '/products', [
+		register_rest_route('woonoow/v1', '/products', [
 			'methods' => 'GET',
-			'callback' => $callback,
+			'callback' => [__CLASS__, 'get_products'],
 			'permission_callback' => [Permissions::class, 'check_admin_permission'],
 		]);
-		error_log('WooNooW ProductsController: GET /products registered: ' . ($result ? 'SUCCESS' : 'FAILED'));
 		
 		// Get single product
 		register_rest_route('woonoow/v1', '/products/(?P<id>\d+)', [
@@ -136,8 +129,6 @@ class ProductsController {
 	 * Get products list with filters
 	 */
 	public static function get_products(WP_REST_Request $request) {
-		error_log('WooNooW ProductsController::get_products() CALLED - START');
-		
 		try {
 			$page = max(1, (int) $request->get_param('page'));
 		$per_page = min(100, max(1, (int) ($request->get_param('per_page') ?: 20)));
@@ -206,12 +197,7 @@ class ProductsController {
 		foreach ($query->posts as $post) {
 			$product = wc_get_product($post->ID);
 			if ($product) {
-				$formatted = self::format_product_list_item($product);
-				// Debug: Log first product to verify structure
-				if (empty($products)) {
-					error_log('WooNooW Debug - First product data: ' . print_r($formatted, true));
-				}
-				$products[] = $formatted;
+				$products[] = self::format_product_list_item($product);
 			}
 		}
 		
@@ -228,14 +214,10 @@ class ProductsController {
 		$response->header('Cache-Control', 'no-cache, no-store, must-revalidate');
 		$response->header('Pragma', 'no-cache');
 		$response->header('Expires', '0');
-		$response->header('X-WooNooW-Version', '2.0'); // Debug header
 		
-		error_log('WooNooW ProductsController::get_products() CALLED - END SUCCESS');
 		return $response;
 		
 		} catch (\Exception $e) {
-			error_log('WooNooW ProductsController::get_products() ERROR: ' . $e->getMessage());
-			error_log('WooNooW ProductsController::get_products() TRACE: ' . $e->getTraceAsString());
 			return new WP_Error('products_error', $e->getMessage(), ['status' => 500]);
 		}
 	}

includes/Api/StoreController.php

@@ -268,17 +268,14 @@ class StoreController extends WP_REST_Controller {
      * @return WP_REST_Response|WP_Error Response object or error
      */
     public function get_customer_settings(WP_REST_Request $request) {
-        error_log('WooNooW: get_customer_settings called');
         try {
             $settings = CustomerSettingsProvider::get_settings();
-            error_log('WooNooW: Customer settings retrieved: ' . print_r($settings, true));
             
             $response = rest_ensure_response($settings);
             $response->header('Cache-Control', 'max-age=60');
             
             return $response;
         } catch (\Exception $e) {
-            error_log('WooNooW: get_customer_settings exception: ' . $e->getMessage());
             return new WP_Error(
                 'get_customer_settings_failed',
                 $e->getMessage(),