feat: 实现教师资料更新、操作日志和系统设置功能

新增教师资料更新功能，包括个人信息修改和密码更新
添加操作日志记录系统，记录用户关键操作
实现系统设置模块，支持动态配置系统参数
重构数据库模型，新增教师表和系统设置表
优化成绩录入逻辑，支持平时分、期中和期末成绩计算
添加数据导出功能，支持学生、教师和成绩数据导出
完善管理员后台，增加统计图表和操作日志查看

backend/models/Course.js

@@ -2,10 +2,15 @@ const db = require('../config/database');
 
 class Course {
     static async findByTeacherId(teacherId) {
-        return await db.query(
-            'SELECT * FROM courses WHERE teacher_id = ? ORDER BY course_code',
-            [teacherId]
-        );
+        const sql = `
+            SELECT c.*, cl.class_name, 
+                   (SELECT COUNT(*) FROM students s WHERE s.class = cl.class_name) as student_count
+            FROM courses c
+            LEFT JOIN classes cl ON c.class_id = cl.id
+            WHERE c.teacher_id = ?
+            ORDER BY c.course_code
+        `;
+        return await db.query(sql, [teacherId]);
     }
     
     static async findById(id) {
@@ -37,6 +42,28 @@ class Course {
         `;
         return await db.query(sql, [studentId]);
     }
+
+    static async getClasses() {
+        return await db.query('SELECT * FROM classes');
+    }
+
+    static async create(data) {
+        const { course_name, course_code, credit, teacher_id, semester, class_id, category } = data;
+        const sql = `INSERT INTO courses (course_name, course_code, credit, teacher_id, semester, class_id, category) VALUES (?, ?, ?, ?, ?, ?, ?)`;
+        const result = await db.query(sql, [course_name, course_code, credit, teacher_id, semester, class_id, category]);
+        return result.insertId;
+    }
+
+    static async update(id, data) {
+        const { course_name, course_code, credit, semester, class_id } = data;
+        const sql = `
+            UPDATE courses 
+            SET course_name = ?, course_code = ?, credit = ?, semester = ?, class_id = ?
+            WHERE id = ?
+        `;
+        const result = await db.query(sql, [course_name, course_code, credit, semester, class_id, id]);
+        return result.affectedRows > 0;
+    }
 }
 
 module.exports = Course;