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/components/messages/ChatItem.vue

@@ -0,0 +1,68 @@
+<template>
+  <div
+    class="flex items-center gap-3 p-3 cursor-pointer transition-colors hover:bg-[var(--wa-bg-light)]"
+    :class="{ 'bg-[var(--wa-bg-light)]': active }"
+    @click="$emit('click')"
+  >
+    <UAvatar
+      :alt="chat.name"
+      size="md"
+      :src="chat.profilePicture"
+    />
+
+    <div class="flex-1 min-w-0">
+      <div class="flex items-center justify-between">
+        <p class="font-medium text-[var(--wa-text)] truncate">{{ chat.name }}</p>
+        <span class="text-xs text-[var(--wa-text-muted)]">{{ formatTime(chat.lastMessageAt) }}</span>
+      </div>
+      <div class="flex items-center justify-between">
+        <p class="text-sm text-[var(--wa-text-muted)] truncate">{{ chat.lastMessage }}</p>
+        <span
+          v-if="chat.unreadCount > 0"
+          class="bg-[var(--wa-green-light)] text-white text-xs rounded-full px-2 py-0.5"
+        >
+          {{ chat.unreadCount }}
+        </span>
+      </div>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+interface Chat {
+  id: string
+  name: string
+  jid: string
+  profilePicture?: string
+  lastMessage: string
+  lastMessageAt: Date
+  unreadCount: number
+}
+
+interface Props {
+  chat: Chat
+  active?: boolean
+}
+
+defineProps<Props>()
+defineEmits<{
+  click: []
+}>()
+
+const formatTime = (date: Date) => {
+  const d = new Date(date)
+  const now = new Date()
+  const diff = now.getTime() - d.getTime()
+  const days = Math.floor(diff / (1000 * 60 * 60 * 24))
+
+  if (days === 0) {
+    return d.toLocaleTimeString('es-AR', { hour: '2-digit', minute: '2-digit' })
+  } else if (days === 1) {
+    return 'Ayer'
+  } else if (days < 7) {
+    return d.toLocaleDateString('es-AR', { weekday: 'short' })
+  } else {
+    return d.toLocaleDateString('es-AR', { day: '2-digit', month: '2-digit' })
+  }
+}
+</script>