feat: 多班级版 v2.0 - Go后端重写 + 43轮代码审查

- 后端从 Python FastAPI 重写为 Go Gin（端口 56789）
- 多班级完全隔离
- 超级管理员独立登录
- 课代表作业管理、排行榜分项排行
- 角色加减分上下限可配置
- 家长改密功能（可开关）
- 周度/月度重置功能
- MySQL 5.7 兼容
- 43轮代码审查+全部修复
- Apache 2.0 许可证

frontend/assets/js/rankings.js

@@ -0,0 +1,59 @@
+/**
+ * 多班级版班级管理系统 - 排行榜JS
+ * 
+ * 开发者: Canglan
+ * 版权归属: Sea Network Technology Studio
+ * 
+ * 版权所有 © Sea Network Technology Studio
+ */
+
+(function() {
+'use strict';
+
+let currentType = 'conduct';
+
+async function loadRankings(type) {
+    const res = await apiGet('/api/admin/rankings', { type: type, limit: 50 });
+    if (res && res.success && res.data) {
+        const rankings = res.data.ranking || [];
+        let html = '';
+        if (rankings.length === 0) {
+            html = '<tr><td colspan="4" style="text-align:center;">暂无排行数据</td></tr>';
+        } else {
+            rankings.forEach(function(item, index) {
+                let rankClass = '';
+                if (index === 0) rankClass = 'rank-gold';
+                else if (index === 1) rankClass = 'rank-silver';
+                else if (index === 2) rankClass = 'rank-bronze';
+
+                let pointsText = Number(item.points !== undefined ? item.points : (item.total_points || 0));
+                if (pointsText > 0) {
+                    pointsText = '+' + pointsText;
+                }
+
+                html += '<tr>' +
+                    '<td><span class="rank-badge ' + rankClass + '">' + (index + 1) + '</span></td>' +
+                    '<td>' + escapeHtml(item.student_no || '-') + '</td>' +
+                    '<td>' + escapeHtml(item.name || '-') + '</td>' +
+                    '<td><span class="record-points ' + (pointsText > 0 ? 'plus' : (pointsText < 0 ? 'minus' : '')) + '">' + pointsText + '</span></td>' +
+                '</tr>';
+            });
+        }
+        document.getElementById('rankingList').innerHTML = html;
+    } else {
+        document.getElementById('rankingList').innerHTML = '<tr><td colspan="4" style="text-align:center;">加载失败</td></tr>';
+    }
+}
+
+window.switchTab = function(type, btn) {
+    currentType = type;
+    document.querySelectorAll('.tab-btn').forEach(function(b) { b.classList.remove('active'); });
+    btn.classList.add('active');
+    loadRankings(type);
+};
+
+document.addEventListener('DOMContentLoaded', function() {
+    loadRankings(currentType);
+});
+
+})();