feat(学生): 添加成绩分析功能及密码修改功能

- 新增成绩分析页面，包含GPA趋势图、成绩分布图和学分进度
- 实现学生密码修改功能，包括前端表单和后端验证逻辑
- 添加课程类别分析功能，展示不同类别课程的GPA表现
- 优化学生仪表板和课程页面导航链接
- 增加数据加载状态提示和错误处理

backend/routes/auth.js

@@ -1,10 +1,12 @@
 const express = require('express');
 const router = express.Router();
 const AuthController = require('../controllers/authController');
+const { requireAuth } = require('../middleware/auth');
 
 router.post('/login', AuthController.login);
 router.post('/register', AuthController.register);
 router.post('/logout', AuthController.logout);
 router.get('/me', AuthController.getCurrentUser);
+router.put('/update-password', requireAuth, AuthController.updatePassword);
 
 module.exports = router;

backend/routes/student.js

@@ -5,6 +5,7 @@ const { requireAuth, requireRole } = require('../middleware/auth');
 
 router.get('/courses', requireAuth, requireRole(['student']), StudentController.getCourses);
 router.get('/courses/:id', requireAuth, requireRole(['student']), StudentController.getCourseDetails);
+router.get('/statistics', requireAuth, requireRole(['student']), StudentController.getGradeStatistics);
 router.get('/grades', requireAuth, requireRole(['student']), StudentController.getGrades);
 router.get('/grades/:id', requireAuth, requireRole(['student']), StudentController.getGradeDetails);