feat: allow sending attachments in new conversations

- replace existing combobox selects with common component selectcombobox.vue

frontend/src/components/button/CloseButton.vue

@@ -0,0 +1,24 @@
+<template>
+  <Button
+    variant="ghost"
+    @click.prevent="onClose"
+    size="xs"
+    class="text-gray-400 dark:text-gray-500 hover:text-gray-600 hover:bg-gray-100 dark:hover:bg-gray-800 w-6 h-6 p-0"
+  >
+    <slot>
+      <X size="16" />
+    </slot>
+  </Button>
+</template>
+
+<script setup>
+import { Button } from '@/components/ui/button'
+import { X } from 'lucide-vue-next'
+
+defineProps({
+  onClose: {
+    type: Function,
+    required: true
+  }
+})
+</script>