fix: Admin SPA loading and remove MailQueue debug logs

Problem 1: Admin SPA not loading in production
Root Cause: Vite builds require type='module' attribute on script tags
Solution: Added script_loader_tag filter to add type='module' to admin SPA script

Problem 2: Annoying MailQueue debug logs in console
Solution: Removed all error_log statements from MailQueue class
- Removed init() debug log
- Removed enqueue() debug log
- Removed all sendNow() debug logs (was 10+ lines)
- Kept only essential one-line log after successful send

Changes:
- includes/Admin/Assets.php: Add type='module' to wnw-admin script
- includes/Core/Mail/MailQueue.php: Remove debug logging noise

Result:
✅ Admin SPA now loads with proper ES module support
✅ MailQueue logs removed from console
✅ Email functionality still works (kept minimal logging)

Note: Production zip is 21M (includes .vite manifests and dynamic imports)

includes/Admin/Assets.php

@@ -176,6 +176,15 @@ class Assets {
 
         if (file_exists($dist_dir . $js)) {
             wp_enqueue_script('wnw-admin', $base_url . $js, ['wp-element'], $ver_js, true);
+            
+            // Add type="module" attribute for Vite build
+            add_filter('script_loader_tag', function($tag, $handle, $src) {
+                if ($handle === 'wnw-admin') {
+                    $tag = str_replace('<script ', '<script type="module" ', $tag);
+                }
+                return $tag;
+            }, 10, 3);
+            
             self::localize_runtime('wnw-admin');
         }
     }