Webhooks: Completar integracion backend-frontend

- Inicializar webhookDispatcher en plugin de servidor
- Conectar pagina de webhooks con API
- Agregar selector de instancias en formulario
- Corregir bug en toast de handleSaved

app/components/webhooks/WebhookFormModal.vue

@@ -93,9 +93,15 @@ interface Webhook {
   instanceId?: string
 }
 
+interface Instance {
+  id: string
+  name: string
+}
+
 interface Props {
   open: boolean
   webhook?: Webhook | null
+  instances?: Instance[]
 }
 
 const props = defineProps<Props>()
@@ -129,8 +135,11 @@ const availableEvents = [
   { value: 'instance.qr', label: 'QR disponible' }
 ]
 
-// TODO: Cargar instancias reales
-const instanceOptions = ref<any[]>([])
+// Instance options for selector
+const instanceOptions = computed(() => [
+  { label: 'Todas las instancias', value: null },
+  ...(props.instances || []).map(i => ({ label: i.name, value: i.id }))
+])
 
 const isValid = computed(() => {
   return form.value.name.trim() && form.value.url.trim() && form.value.events.length > 0