fix: eliminar polling get_notifications en index.php + debug wamid en broadcast

- index.php: NotificationManager simplificado a stub vacío.
  Los elementos notification-bell / global-notification-toasts no existen en el
  markup → el setInterval cada 7s solo generaba tráfico inútil a get_notifications.php
  Las notificaciones ya se manejan vía SSE en conversations.php

- send_broadcast.php: exponer debug_wamids en respuesta (wamid, wa_status, wa_contact)
  para saber exactamente qué devuelve WhatsApp por cada destinatario.
  Agregar dryRun log del payload completo al error_log para diagnóstico de
  mensajes que WhatsApp acepta (200+wamid) pero no entrega.

api/send_broadcast.php

@@ -90,6 +90,7 @@ try {
     $sentCount = 0;
     $errorCount = 0;
     $errors = [];
+    $debugWamids = [];
     
     foreach ($users as $user) {
         try {
@@ -185,6 +186,19 @@ try {
                     $processedVariables,
                     $headerParams
                 );
+
+                // Log payload para diagnóstico
+                $dryPayload = $whatsappService->sendTemplateMessage(
+                    $user['phone_number'],
+                    $template['template_name'] ?? $template['name'],
+                    $template['language_code'] ?? 'es',
+                    $processedVariables,
+                    $headerParams,
+                    null, null, true   // dryRun=true
+                );
+                error_log("=== BROADCAST TEMPLATE PAYLOAD (para " . $user['phone_number'] . ") ===");
+                error_log(json_encode($dryPayload, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT));
+                error_log("=== FIN PAYLOAD ===");
                 
                 // Construir contenido para BD (reemplazar variables en body_text)
                 $messageContent = $template['body_text'] ?? $template['name'];
@@ -218,6 +232,12 @@ try {
 
             if ($isSuccess) {
                 $sentCount++;
+                $debugWamids[] = [
+                    'phone'      => $user['phone_number'],
+                    'wamid'      => $sentMessageId,
+                    'wa_status'  => $response['messages'][0]['message_status'] ?? 'accepted',
+                    'wa_contact' => $response['contacts'][0]['wa_id'] ?? null,
+                ];
                 
                 // Guardar mensaje en BD
                 $db->insert('conversations', [
@@ -258,7 +278,8 @@ try {
         'total_users' => count($users),
         'selection_type' => $selectionType,
         'message_type' => $messageType,
-        'errors' => $errorCount > 0 ? $errors : null
+        'errors' => $errorCount > 0 ? $errors : null,
+        'debug_wamids' => $debugWamids ?? []
     ]);
     
 } catch (Exception $e) {