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/pages/Dashboard.vue

@@ -0,0 +1,126 @@
+<template>
+  <n-flex class="container" :wrap="false">
+    <div class="sidebar">
+      <div class="back-btn" @click="() => goHome($router, taskTab, step)">
+        ← 返回
+      </div>
+      <n-divider style="margin: 8px 0" />
+      <div
+        v-for="item in menu"
+        :key="item.label"
+        :class="['nav-item', { active: $route.name === item.route.name }]"
+        @click="$router.push(item.route)"
+      >
+        {{ item.label }}
+      </div>
+    </div>
+    <div class="content">
+      <router-view></router-view>
+    </div>
+  </n-flex>
+</template>
+<script lang="ts" setup>
+import { computed } from "vue"
+import { taskTab } from "../store/task"
+import { step } from "../store/tutorial"
+import { roleAdmin, roleSuper } from "../store/user"
+import { goHome } from "../utils/helper"
+
+const menu = computed(() =>
+  [
+    {
+      label: "教程",
+      route: { name: "tutorial-editor", params: { display: step.value } },
+      show: roleSuper.value,
+    },
+    {
+      label: "挑战",
+      route: { name: "challenge-editor", params: { display: 0 } },
+      show: roleAdmin.value || roleSuper.value,
+    },
+    {
+      label: "用户",
+      route: { name: "user-manage", params: { page: 1 } },
+      show: roleSuper.value,
+    },
+    {
+      label: "工坊",
+      route: { name: "showcase-manage" },
+      show: roleSuper.value,
+    },
+    {
+      label: "成绩",
+      route: { name: "gradebook" },
+      show: roleSuper.value,
+    },
+    {
+      label: "提交",
+      route: { name: "submissions", params: { page: 1 } },
+      show: roleAdmin.value || roleSuper.value,
+    },
+  ].filter((item) => item.show),
+)
+</script>
+<style scoped>
+.container {
+  height: 100vh;
+  width: 100vw;
+  box-sizing: border-box;
+}
+
+.sidebar {
+  width: 110px;
+  min-width: 110px;
+  padding: 12px 8px;
+  border-right: 1px solid #efeff5;
+  background: #fafafa;
+  display: flex;
+  flex-direction: column;
+  gap: 2px;
+}
+
+.back-btn {
+  padding: 7px 10px;
+  font-size: 13px;
+  color: #888;
+  cursor: pointer;
+  border-radius: 6px;
+  transition:
+    background-color 0.15s,
+    color 0.15s;
+  user-select: none;
+}
+
+.back-btn:hover {
+  background-color: #f0f0f0;
+  color: #444;
+}
+
+.nav-item {
+  padding: 8px 10px;
+  border-radius: 6px;
+  font-size: 14px;
+  cursor: pointer;
+  color: #444;
+  transition:
+    background-color 0.15s,
+    color 0.15s;
+  user-select: none;
+}
+
+.nav-item:hover {
+  background-color: #f0f0f0;
+}
+
+.nav-item.active {
+  background-color: #e8f8f0;
+  color: #18a058;
+  font-weight: 500;
+}
+
+.content {
+  flex: 1;
+  box-sizing: border-box;
+  overflow: hidden;
+}
+</style>