fix : add missing TuiAlert component

TuiAlert.vue was referenced by Main.vue but never committed, breaking the Docker/CI build.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/components/TuiAlert.vue

@@ -0,0 +1,20 @@
+<script setup>
+defineProps({
+  message: {
+    type: String,
+    required: true
+  }
+});
+
+defineEmits(['close']);
+</script>
+
+<template>
+  <div class="tui-alert-window">
+    <div class="tui-alert-header">
+      <span>[SYSTEM ALERT]</span>
+    </div>
+    <div class="tui-alert-body">{{ message }}</div>
+    <button class="tui-alert-btn" @click="$emit('close')">확인</button>
+  </div>
+</template>