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

app/composables/useInstances.ts

@@ -0,0 +1,124 @@
+/**
+ * Composable for managing WhatsApp instances
+ */
+
+export interface Instance {
+  id: string
+  name: string
+  phoneNumber: string | null
+  status: 'disconnected' | 'connecting' | 'connected' | 'qr_ready' | 'pairing'
+  qrCode: string | null
+  pairingCode: string | null
+  lastConnectedAt: Date | null
+  createdAt: Date
+}
+
+export const useInstances = () => {
+  const instances = useState<Instance[]>('instances', () => [])
+  const loading = useState('instancesLoading', () => false)
+  const error = useState<string | null>('instancesError', () => null)
+
+  const fetchInstances = async () => {
+    loading.value = true
+    error.value = null
+    try {
+      const data = await $fetch<Instance[]>('/api/instances')
+      instances.value = data
+    } catch (e) {
+      error.value = (e as Error).message
+      console.error('Error fetching instances:', e)
+    } finally {
+      loading.value = false
+    }
+  }
+
+  const createInstance = async (name: string): Promise<Instance | null> => {
+    try {
+      const instance = await $fetch<Instance>('/api/instances', {
+        method: 'POST',
+        body: { name }
+      })
+      instances.value.push(instance)
+      return instance
+    } catch (e) {
+      console.error('Error creating instance:', e)
+      throw e
+    }
+  }
+
+  const deleteInstance = async (id: string) => {
+    try {
+      await $fetch(`/api/instances/${id}`, { method: 'DELETE' })
+      instances.value = instances.value.filter(i => i.id !== id)
+    } catch (e) {
+      console.error('Error deleting instance:', e)
+      throw e
+    }
+  }
+
+  const connectInstance = async (id: string): Promise<{ qrCode: string | null; status: string }> => {
+    const result = await $fetch<{ qrCode: string | null; status: string }>(`/api/instances/${id}/connect`, {
+      method: 'POST'
+    })
+
+    // Update local state
+    const idx = instances.value.findIndex(i => i.id === id)
+    if (idx !== -1) {
+      instances.value[idx].status = result.status as Instance['status']
+      instances.value[idx].qrCode = result.qrCode
+    }
+
+    return result
+  }
+
+  const disconnectInstance = async (id: string) => {
+    await $fetch(`/api/instances/${id}/disconnect`, { method: 'POST' })
+
+    // Update local state
+    const idx = instances.value.findIndex(i => i.id === id)
+    if (idx !== -1) {
+      instances.value[idx].status = 'disconnected'
+      instances.value[idx].qrCode = null
+    }
+  }
+
+  const getQRCode = async (id: string): Promise<string | null> => {
+    const result = await $fetch<{ qrCode: string | null }>(`/api/instances/${id}/qr`)
+    return result.qrCode
+  }
+
+  const requestPairingCode = async (id: string, phoneNumber: string): Promise<string> => {
+    const result = await $fetch<{ code: string }>(`/api/instances/${id}/pairing-code`, {
+      method: 'POST',
+      body: { phoneNumber }
+    })
+    return result.code
+  }
+
+  const getInstanceStatus = async (id: string) => {
+    return await $fetch(`/api/instances/${id}/status`)
+  }
+
+  // Computed helpers
+  const connectedCount = computed(() =>
+    instances.value.filter(i => i.status === 'connected').length
+  )
+
+  const totalCount = computed(() => instances.value.length)
+
+  return {
+    instances,
+    loading,
+    error,
+    fetchInstances,
+    createInstance,
+    deleteInstance,
+    connectInstance,
+    disconnectInstance,
+    getQRCode,
+    requestPairingCode,
+    getInstanceStatus,
+    connectedCount,
+    totalCount
+  }
+}