Fix: fetchMessageHistory con evento SSE y logs de debug

- Agregar logs detallados en /api/debug/history/fetch para diagnosticar
- Emitir evento SSE 'history.synced' cuando llegan mensajes del historial
- Frontend ahora escucha el evento SSE en vez de timeout fijo de 3 segundos
- Agregar script y documentación para referencia de Baileys message history

server/api/debug/history/fetch.post.ts

@@ -26,13 +26,31 @@ export default defineEventHandler(async (event) => {
     throw createError({ statusCode: 400, message: 'Instance not connected' })
   }
 
+  // Verificar que el método existe
+  if (typeof socket.fetchMessageHistory !== 'function') {
+    console.error('[History] fetchMessageHistory method not available on socket')
+    console.error('[History] Available methods:', Object.keys(socket).filter(k => typeof (socket as any)[k] === 'function').join(', '))
+    throw createError({ statusCode: 500, message: 'fetchMessageHistory not available on this Baileys version' })
+  }
+
+  // Log de parámetros
+  console.log('[History] Requesting history with params:', {
+    instanceId,
+    count,
+    oldestMsgKey: oldestMsgKey ? JSON.stringify(oldestMsgKey) : 'undefined',
+    oldestMsgTimestamp: oldestMsgTimestamp || 'undefined'
+  })
+
   try {
-    await socket.fetchMessageHistory(count, oldestMsgKey, oldestMsgTimestamp)
+    const result = await socket.fetchMessageHistory(count, oldestMsgKey, oldestMsgTimestamp)
+    console.log('[History] fetchMessageHistory returned:', result)
     return {
       success: true,
+      result,
       message: `Requested ${count} messages from history. Check messaging-history.set event for results.`
     }
   } catch (error) {
+    console.error('[History] fetchMessageHistory error:', error)
     throw createError({
       statusCode: 500,
       message: `Failed to fetch message history: ${(error as Error).message}`