feat(login): 添加记住我登录功能

前端新增记住我勾选框，登录页挂载时自动恢复已保存的用户名，勾选时将用户名存入本地存储并在登录请求中携带对应参数；后端新增rememberMe参数处理逻辑，配置7天免登录的JWT有效期，重载JWT工具类以支持自定义令牌过期时间

frontend/src/types/index.ts

@@ -14,6 +14,7 @@ export interface User {
 export interface LoginRequest {
   username: string
   password: string
+  rememberMe?: boolean
 }
 
 export interface LoginResponse {

frontend/src/views/Login.vue

@@ -21,6 +21,9 @@
             @keyup.enter="handleLogin"
           />
         </el-form-item>
+        <el-form-item>
+          <el-checkbox v-model="remember">记住我（7天免登录）</el-checkbox>
+        </el-form-item>
         <el-form-item>
           <el-button type="primary" size="large" :loading="loading" @click="handleLogin" class="login-btn">
             登录
@@ -32,7 +35,7 @@
 </template>
 
 <script setup lang="ts">
-import { ref, reactive } from 'vue'
+import { ref, reactive, onMounted } from 'vue'
 import { useRouter } from 'vue-router'
 import { ElMessage, type FormInstance, type FormRules } from 'element-plus'
 import { useUserStore } from '@/stores/user'
@@ -49,6 +52,16 @@ const loginForm = reactive({
   password: ''
 })
 
+const remember = ref(false)
+
+onMounted(() => {
+  const savedUsername = localStorage.getItem('remember-username')
+  if (savedUsername) {
+    loginForm.username = savedUsername
+    remember.value = true
+  }
+})
+
 const rules: FormRules = {
   username: [{ required: true, message: '请输入用户名', trigger: 'blur' }],
   password: [{ required: true, message: '请输入密码', trigger: 'blur' }]
@@ -64,8 +77,15 @@ const handleLogin = async () => {
         const hashedPassword = await hashPassword(loginForm.password)
         await userStore.login({
           username: loginForm.username,
-          password: hashedPassword
+          password: hashedPassword,
+          rememberMe: remember.value
         })
+        // 记住用户名（勾选"记住我"时保存，否则清除）
+        if (remember.value) {
+          localStorage.setItem('remember-username', loginForm.username)
+        } else {
+          localStorage.removeItem('remember-username')
+        }
         ElMessage.success('登录成功')
         router.push('/')
       } catch (error) {