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

app/pages/messages/index.vue

@@ -395,10 +395,10 @@ const fetchWhatsAppHistory = async () => {
   if (!selectedInstance.value?.value || !selectedChat.value) return
 
   loadingWhatsAppHistory.value = true
-  try {
-    const instanceId = selectedInstance.value.value
-    const chatId = selectedChat.value.id
+  const instanceId = selectedInstance.value.value
+  const chatId = selectedChat.value.id
 
+  try {
     // Get the oldest message from local DB
     const oldest = await $fetch<{
       hasMessages: boolean
@@ -406,6 +406,23 @@ const fetchWhatsAppHistory = async () => {
       timestamp: number | null
     }>(`/api/messages/${instanceId}/${chatId}/oldest`)
 
+    // Create a promise that resolves when history.synced event arrives
+    const historyPromise = new Promise<{ messagesCount: number; timeout?: boolean }>((resolve) => {
+      // Set up listener for history.synced event
+      const cleanup = on('history.synced', (data) => {
+        if (data.instanceId === instanceId) {
+          cleanup() // Remove listener
+          resolve({ messagesCount: data.messagesCount })
+        }
+      })
+
+      // Timeout de seguridad (15 segundos)
+      setTimeout(() => {
+        cleanup() // Remove listener
+        resolve({ messagesCount: 0, timeout: true })
+      }, 15000)
+    })
+
     // Request history from WhatsApp
     if (!oldest.hasMessages) {
       // No messages in DB, request without reference
@@ -429,10 +446,18 @@ const fetchWhatsAppHistory = async () => {
       })
     }
 
-    // Wait for history sync to complete and reload
-    await new Promise(r => setTimeout(r, 3000))
-    await reloadMessages()
-    hasMoreMessages.value = true
+    // Wait for history sync event or timeout
+    const result = await historyPromise
+
+    if (result.timeout) {
+      console.log('[History] Timeout waiting for history sync - WhatsApp may not have more messages')
+    } else if (result.messagesCount > 0) {
+      console.log(`[History] Received ${result.messagesCount} messages from history sync`)
+      await reloadMessages()
+      hasMoreMessages.value = true
+    } else {
+      console.log('[History] No messages received from history sync')
+    }
   } catch (e) {
     console.error('Error fetching WhatsApp history:', e)
   } finally {