chore: 将前端移动到 client/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/components/submissions/CodeModal.vue

@@ -0,0 +1,42 @@
+<template>
+  <n-modal
+    preset="card"
+    :show="show"
+    style="max-width: 60%"
+    @update:show="$emit('update:show', $event)"
+  >
+    <template #header>
+      <n-flex align="center">
+        <span>前端代码</span>
+        <n-button tertiary @click="$emit('copy-to-editor')"
+          >复制到编辑框</n-button
+        >
+      </n-flex>
+    </template>
+    <n-tabs animated type="segment">
+      <n-tab-pane name="html" tab="html">
+        <n-code :code="html" language="html" word-wrap />
+      </n-tab-pane>
+      <n-tab-pane name="css" tab="css">
+        <n-code :code="css" language="css" word-wrap />
+      </n-tab-pane>
+      <n-tab-pane v-if="!!js" name="js" tab="js">
+        <n-code :code="js" language="js" word-wrap />
+      </n-tab-pane>
+    </n-tabs>
+  </n-modal>
+</template>
+
+<script setup lang="ts">
+defineProps<{
+  show: boolean
+  html: string
+  css: string
+  js: string
+}>()
+
+defineEmits<{
+  "update:show": [value: boolean]
+  "copy-to-editor": []
+}>()
+</script>