feat: KPL v1.5.0 功能迭代

1. 奖章条件优化
- 修复统计查询 SQL 语法
- 添加按类别检查奖章方法

2. 移动端适配
- 登录页、课程中心、课程详情
- 考试页面、成长路径、排行榜

3. 证书系统
- 数据库模型和迁移脚本
- 证书颁发/列表/下载/验证 API
- 前端证书列表页面

4. 数据大屏
- 企业级/团队级数据 API
- ECharts 可视化大屏页面

backend/migrations/add_certificate_system.sql

@@ -0,0 +1,166 @@
+-- ================================================================
+-- 证书系统数据库迁移脚本
+-- 创建日期: 2026-01-29
+-- 功能: 添加证书模板表和用户证书表
+-- ================================================================
+
+-- 事务开始
+START TRANSACTION;
+
+-- ================================================================
+-- 1. 创建证书模板表
+-- ================================================================
+CREATE TABLE IF NOT EXISTS certificate_templates (
+    id INT PRIMARY KEY AUTO_INCREMENT,
+    name VARCHAR(100) NOT NULL COMMENT '模板名称',
+    type ENUM('course', 'exam', 'achievement') NOT NULL COMMENT '证书类型: course=课程结业, exam=考试合格, achievement=成就证书',
+    background_url VARCHAR(500) COMMENT '证书背景图URL',
+    template_html TEXT COMMENT 'HTML模板内容',
+    template_style TEXT COMMENT 'CSS样式',
+    is_active BOOLEAN DEFAULT TRUE COMMENT '是否启用',
+    sort_order INT DEFAULT 0 COMMENT '排序顺序',
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    INDEX idx_type (type),
+    INDEX idx_is_active (is_active)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='证书模板表';
+
+-- ================================================================
+-- 2. 创建用户证书表
+-- ================================================================
+CREATE TABLE IF NOT EXISTS user_certificates (
+    id INT PRIMARY KEY AUTO_INCREMENT,
+    user_id INT NOT NULL COMMENT '用户ID',
+    template_id INT NOT NULL COMMENT '模板ID',
+    certificate_no VARCHAR(50) UNIQUE NOT NULL COMMENT '证书编号 KPL-年份-序号',
+    title VARCHAR(200) NOT NULL COMMENT '证书标题',
+    description TEXT COMMENT '证书描述/成就说明',
+    issued_at DATETIME DEFAULT CURRENT_TIMESTAMP COMMENT '颁发时间',
+    valid_until DATETIME COMMENT '有效期至（NULL表示永久）',
+    
+    -- 关联信息
+    course_id INT COMMENT '关联课程ID',
+    exam_id INT COMMENT '关联考试ID',
+    badge_id INT COMMENT '关联奖章ID',
+    
+    -- 成绩信息
+    score DECIMAL(5,2) COMMENT '考试分数',
+    completion_rate DECIMAL(5,2) COMMENT '完成率',
+    
+    -- 生成的文件
+    pdf_url VARCHAR(500) COMMENT 'PDF文件URL',
+    image_url VARCHAR(500) COMMENT '分享图片URL',
+    
+    -- 元数据
+    meta_data JSON COMMENT '扩展元数据',
+    
+    created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    updated_at DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    
+    FOREIGN KEY (user_id) REFERENCES users(id) ON DELETE CASCADE,
+    FOREIGN KEY (template_id) REFERENCES certificate_templates(id),
+    INDEX idx_user_id (user_id),
+    INDEX idx_certificate_no (certificate_no),
+    INDEX idx_course_id (course_id),
+    INDEX idx_exam_id (exam_id),
+    INDEX idx_issued_at (issued_at)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='用户证书表';
+
+-- ================================================================
+-- 3. 插入默认证书模板
+-- ================================================================
+INSERT INTO certificate_templates (name, type, template_html, template_style, is_active, sort_order) VALUES
+-- 课程结业证书模板
+('课程结业证书', 'course', 
+'<div class="certificate">
+  <div class="header">
+    <div class="logo">考培练系统</div>
+    <h1>结业证书</h1>
+  </div>
+  <div class="body">
+    <p class="recipient">兹证明 <strong>{{user_name}}</strong></p>
+    <p class="content">已完成课程《{{course_name}}》的全部学习内容</p>
+    <p class="completion">完成率：{{completion_rate}}%</p>
+    <p class="date">颁发日期：{{issue_date}}</p>
+  </div>
+  <div class="footer">
+    <div class="cert-no">证书编号：{{certificate_no}}</div>
+    <div class="qrcode">{{qrcode}}</div>
+  </div>
+</div>',
+'.certificate { width: 800px; height: 600px; padding: 40px; background: linear-gradient(135deg, #f5f7fa 0%, #e4e9f2 100%); font-family: "Microsoft YaHei", sans-serif; }
+.header { text-align: center; margin-bottom: 30px; }
+.header .logo { font-size: 24px; color: #667eea; font-weight: bold; }
+.header h1 { font-size: 36px; color: #333; margin: 20px 0; }
+.body { text-align: center; padding: 30px 60px; }
+.body .recipient { font-size: 20px; margin-bottom: 20px; }
+.body .content { font-size: 18px; color: #555; margin-bottom: 15px; }
+.body .completion { font-size: 16px; color: #667eea; }
+.body .date { font-size: 14px; color: #888; margin-top: 30px; }
+.footer { display: flex; justify-content: space-between; align-items: center; margin-top: 40px; }
+.cert-no { font-size: 12px; color: #999; }
+.qrcode { width: 80px; height: 80px; }',
+TRUE, 1),
+
+-- 考试合格证书模板
+('考试合格证书', 'exam',
+'<div class="certificate exam-cert">
+  <div class="header">
+    <div class="logo">考培练系统</div>
+    <h1>考试合格证书</h1>
+  </div>
+  <div class="body">
+    <p class="recipient">兹证明 <strong>{{user_name}}</strong></p>
+    <p class="content">在《{{exam_name}}》考试中成绩合格</p>
+    <div class="score-badge">
+      <span class="score">{{score}}</span>
+      <span class="unit">分</span>
+    </div>
+    <p class="date">考试日期：{{exam_date}}</p>
+  </div>
+  <div class="footer">
+    <div class="cert-no">证书编号：{{certificate_no}}</div>
+    <div class="qrcode">{{qrcode}}</div>
+  </div>
+</div>',
+'.certificate.exam-cert { width: 800px; height: 600px; padding: 40px; background: linear-gradient(135deg, #e8f5e9 0%, #c8e6c9 100%); font-family: "Microsoft YaHei", sans-serif; }
+.exam-cert .header h1 { color: #2e7d32; }
+.score-badge { display: inline-block; padding: 20px 40px; background: #fff; border-radius: 50%; box-shadow: 0 4px 20px rgba(0,0,0,0.1); margin: 20px 0; }
+.score-badge .score { font-size: 48px; font-weight: bold; color: #2e7d32; }
+.score-badge .unit { font-size: 18px; color: #666; }',
+TRUE, 2),
+
+-- 成就证书模板
+('成就证书', 'achievement',
+'<div class="certificate achievement-cert">
+  <div class="header">
+    <div class="logo">考培练系统</div>
+    <h1>成就证书</h1>
+  </div>
+  <div class="body">
+    <p class="recipient">兹证明 <strong>{{user_name}}</strong></p>
+    <div class="achievement-icon">{{badge_icon}}</div>
+    <p class="achievement-name">{{badge_name}}</p>
+    <p class="achievement-desc">{{badge_description}}</p>
+    <p class="date">获得日期：{{achieve_date}}</p>
+  </div>
+  <div class="footer">
+    <div class="cert-no">证书编号：{{certificate_no}}</div>
+    <div class="qrcode">{{qrcode}}</div>
+  </div>
+</div>',
+'.certificate.achievement-cert { width: 800px; height: 600px; padding: 40px; background: linear-gradient(135deg, #fff3e0 0%, #ffe0b2 100%); font-family: "Microsoft YaHei", sans-serif; }
+.achievement-cert .header h1 { color: #e65100; }
+.achievement-icon { font-size: 64px; margin: 20px 0; }
+.achievement-name { font-size: 24px; font-weight: bold; color: #e65100; margin: 10px 0; }
+.achievement-desc { font-size: 16px; color: #666; }',
+TRUE, 3);
+
+-- 提交事务
+COMMIT;
+
+-- ================================================================
+-- 验证脚本
+-- ================================================================
+-- SELECT * FROM certificate_templates;
+-- SELECT COUNT(*) AS template_count FROM certificate_templates;