feat: WhatsApp Nucleo con Nuxt 4 + Baileys v7

Reemplazo completo de Evolution API por implementación directa con Baileys.

Características:
- Dashboard completo con Nuxt UI v4
- Soporte para múltiples instancias de WhatsApp
- Conexión via QR code o pairing code
- Persistencia de mensajes en PostgreSQL
- API REST para integraciones externas
- Webhooks con firma HMAC
- SSE para actualizaciones en tiempo real
- Autenticación con Authentik

server/api/messages/[instanceId]/[chatId]/send.post.ts

@@ -0,0 +1,53 @@
+/**
+ * POST /api/messages/:instanceId/:chatId/send
+ * Send a message to a chat (from UI)
+ */
+import { query } from '../../../../utils/database'
+import { baileysManager } from '../../../../services/baileys/manager'
+
+interface SendMessageBody {
+  message: string
+}
+
+export default defineEventHandler(async (event) => {
+  const username = getHeader(event, 'x-authentik-username')
+  if (!username) {
+    throw createError({ statusCode: 401, message: 'Unauthorized' })
+  }
+
+  const instanceId = getRouterParam(event, 'instanceId')
+  const chatId = getRouterParam(event, 'chatId')
+  const body = await readBody<SendMessageBody>(event)
+
+  if (!body.message?.trim()) {
+    throw createError({ statusCode: 400, message: 'Message is required' })
+  }
+
+  // Get chat JID
+  const chatResult = await query<{ jid: string }>(
+    'SELECT jid FROM chats WHERE id = $1 AND instance_id = $2',
+    [chatId, instanceId]
+  )
+
+  if (chatResult.rows.length === 0) {
+    throw createError({ statusCode: 404, message: 'Chat not found' })
+  }
+
+  const jid = chatResult.rows[0].jid
+
+  try {
+    const result = await baileysManager.sendMessage(instanceId!, jid, {
+      text: body.message
+    })
+
+    return {
+      success: true,
+      messageId: result.key.id
+    }
+  } catch (error) {
+    throw createError({
+      statusCode: 500,
+      message: `Failed to send message: ${(error as Error).message}`
+    })
+  }
+})