Feat: Agregar botón para iniciar conversación con número nuevo

- Nuevo endpoint POST /api/messages/:instanceId/new-chat
- Valida que el número esté registrado en WhatsApp
- Crea el chat en la DB si no existe
- Modal en UI para ingresar número de teléfono
- Botón verde "+" junto a la barra de búsqueda

app/pages/messages/index.vue

@@ -70,6 +70,14 @@
               icon="i-lucide-search"
               class="flex-1"
             />
+            <button
+              @click="showNewChatModal = true"
+              class="text-xs px-2 py-2 rounded bg-[var(--wa-green)] hover:bg-[var(--wa-green-dark)] text-white"
+              title="Nueva conversacion"
+              :disabled="!selectedInstance"
+            >
+              <UIcon name="i-lucide-plus" class="w-4 h-4" />
+            </button>
             <button
               @click="showChatsDebug = !showChatsDebug"
               class="text-xs px-2 py-2 rounded bg-gray-700 hover:bg-gray-600 text-gray-300"
@@ -242,6 +250,57 @@
         </template>
       </div>
     </div>
+
+    <!-- New Chat Modal -->
+    <UModal v-model:open="showNewChatModal">
+      <template #content>
+        <div class="p-6 bg-[var(--wa-bg-dark)]">
+          <h3 class="text-lg font-semibold text-[var(--wa-text)] mb-4">
+            Nueva conversación
+          </h3>
+
+          <div class="space-y-4">
+            <div>
+              <label class="block text-sm text-[var(--wa-text-muted)] mb-2">
+                Número de teléfono
+              </label>
+              <UInput
+                v-model="newChatPhoneNumber"
+                placeholder="Ej: 50588887777"
+                icon="i-lucide-phone"
+                class="w-full"
+                @keyup.enter="startNewChat"
+              />
+              <p class="text-xs text-[var(--wa-text-muted)] mt-1">
+                Ingresa el número con código de país, sin espacios ni guiones
+              </p>
+            </div>
+
+            <div v-if="newChatError" class="text-sm text-red-400">
+              {{ newChatError }}
+            </div>
+
+            <div class="flex justify-end gap-2 pt-2">
+              <UButton
+                color="neutral"
+                variant="ghost"
+                @click="closeNewChatModal"
+              >
+                Cancelar
+              </UButton>
+              <UButton
+                color="primary"
+                :loading="newChatLoading"
+                :disabled="!newChatPhoneNumber.trim()"
+                @click="startNewChat"
+              >
+                Iniciar conversación
+              </UButton>
+            </div>
+          </div>
+        </div>
+      </template>
+    </UModal>
   </div>
 </template>
 
@@ -279,6 +338,12 @@ const showDebugPanel = ref(false)
 const showChatsDebug = ref(false)
 const showSelectedChatDebug = ref(false)
 
+// New chat modal state
+const showNewChatModal = ref(false)
+const newChatPhoneNumber = ref('')
+const newChatLoading = ref(false)
+const newChatError = ref('')
+
 // Instance options for selector
 const instanceOptions = computed(() =>
   instances.value
@@ -658,6 +723,54 @@ const handleReact = async (message: any, emoji: string) => {
   }
 }
 
+// New chat modal functions
+const closeNewChatModal = () => {
+  showNewChatModal.value = false
+  newChatPhoneNumber.value = ''
+  newChatError.value = ''
+}
+
+const startNewChat = async () => {
+  if (!selectedInstance.value?.value || !newChatPhoneNumber.value.trim()) return
+
+  newChatLoading.value = true
+  newChatError.value = ''
+
+  try {
+    const result = await $fetch(`/api/messages/${selectedInstance.value.value}/new-chat`, {
+      method: 'POST',
+      body: {
+        phoneNumber: newChatPhoneNumber.value.trim()
+      }
+    })
+
+    if (result.success && result.chat) {
+      // If it's a new chat, add it to the list
+      if (result.isNew) {
+        chats.value.unshift(result.chat)
+      }
+
+      // Select the chat
+      selectedChat.value = result.chat
+
+      // Close the modal
+      closeNewChatModal()
+
+      toast.add({
+        title: result.isNew ? 'Conversación creada' : 'Conversación encontrada',
+        icon: 'i-lucide-check',
+        color: 'success',
+        timeout: 2000
+      })
+    }
+  } catch (e: any) {
+    console.error('Error creating new chat:', e)
+    newChatError.value = e?.data?.message || e?.message || 'Error al crear la conversación'
+  } finally {
+    newChatLoading.value = false
+  }
+}
+
 // Handle typing event from input
 const handleTyping = () => {
   if (!selectedChat.value?.jid || selectedChat.value?.isGroup) return