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/scripts/fix_teachers.js

@@ -0,0 +1,31 @@
+const db = require('../config/database');
+
+async function fixTeachers() {
+    const departments = ['计算机学院', '软件学院', '信息工程学院', '理学院', '外国语学院'];
+    const titles = ['教授', '副教授', '讲师', '助教'];
+    
+    try {
+        const teachers = await db.query('SELECT id FROM teachers');
+        for (let i = 0; i < teachers.length; i++) {
+            const dept = departments[i % departments.length];
+            const title = titles[i % titles.length];
+            const contact = `139${Math.floor(Math.random() * 90000000 + 10000000)}`;
+            
+            await db.query(
+                'UPDATE teachers SET department = ?, title = ?, contact_info = ? WHERE id = ?',
+                [dept, title, contact, teachers[i].id]
+            );
+            
+            // Also sync back to users table's class field if needed (though we'll use teachers table now)
+            await db.query(
+                'UPDATE users SET class = ? WHERE id = ?',
+                [dept, teachers[i].id]
+            );
+        }
+        console.log('教师信息修复完成！');
+    } catch (err) {
+        console.error('修复失败:', err);
+    }
+}
+
+fixTeachers();

backend/scripts/migrate_v2.js

@@ -0,0 +1,48 @@
+const db = require('../config/database');
+
+async function migrate() {
+    try {
+        console.log('Starting migration v2...');
+        
+        // 1. System Settings Table
+        await db.query(`
+            CREATE TABLE IF NOT EXISTS system_settings (
+                key TEXT PRIMARY KEY,
+                value TEXT
+            )
+        `);
+        
+        // Default settings
+        const defaultSettings = [
+            ['system_name', '学校成绩管理系统'],
+            ['current_semester', '2023-2024-2'],
+            ['allow_course_selection', '1'],
+            ['allow_grade_check', '1']
+        ];
+        
+        for (const [key, value] of defaultSettings) {
+            await db.query('INSERT OR IGNORE INTO system_settings (key, value) VALUES (?, ?)', [key, value]);
+        }
+        
+        // 2. Operation Logs Table
+        await db.query(`
+            CREATE TABLE IF NOT EXISTS operation_logs (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                user_id TEXT,
+                operation_type TEXT,
+                operation_target TEXT,
+                description TEXT,
+                ip_address TEXT,
+                created_at TEXT DEFAULT (datetime('now', 'localtime'))
+            )
+        `);
+        
+        console.log('Migration v2 completed successfully.');
+        process.exit(0);
+    } catch (error) {
+        console.error('Migration v2 failed:', error);
+        process.exit(1);
+    }
+}
+
+migrate();

backend/scripts/migrate_v3.js

@@ -0,0 +1,33 @@
+const db = require('../config/database');
+
+async function migrate() {
+    console.log('开始执行 v3 迁移: 创建 teachers 表...');
+    
+    try {
+        await db.query(`
+            CREATE TABLE IF NOT EXISTS teachers (
+                id TEXT PRIMARY KEY,
+                name TEXT NOT NULL,
+                department TEXT,
+                title TEXT,
+                contact_info TEXT,
+                FOREIGN KEY (id) REFERENCES users(id) ON DELETE CASCADE
+            )
+        `);
+
+        // 从 users 表中迁移现有的教师数据
+        const teachers = await db.query('SELECT id, name, class FROM users WHERE role = "teacher"');
+        for (const t of teachers) {
+            await db.query(
+                'INSERT OR IGNORE INTO teachers (id, name, department) VALUES (?, ?, ?)',
+                [t.id, t.name, t.class]
+            );
+        }
+
+        console.log('v3 迁移成功！');
+    } catch (err) {
+        console.error('v3 迁移失败:', err);
+    }
+}
+
+migrate();