feat(学生): 添加学生课程管理功能

- 新增我的课程页面及路由
- 实现课程列表和详情查看功能
- 更新导航链接指向新页面
- 添加成绩详情模态框
- 完善相关后端接口和服务

backend/models/Score.js

@@ -22,7 +22,7 @@ class Score {
                    s.usual_score, s.midterm_score, s.final_score, s.total_score as score,
                    s.grade_point, s.grade_level, s.created_at, s.remark,
                    c.course_code, c.course_name, c.credit, c.semester,
-                   u.name as teacher_name, u.email as teacher_email,
+                   u.name as teacher_name,
                    st.id as student_number, st.class as class_name
             FROM grades s
             JOIN courses c ON s.course_id = c.id