feat(admin): 添加系统健康检测功能

新增管理员健康检测面板，可检测以下配置项：
- 安全配置：JWT密钥、CORS、HTTPS、管理员账号、登录防爆破
- 服务状态：SMTP邮件、数据库连接、存储目录
- 运行配置：反向代理支持、Node环境

修改文件：
- backend/auth.js: 新增 isJwtSecretSecure() 函数
- backend/server.js: 新增 /api/admin/health-check API
- frontend/app.js: 新增健康检测数据和方法
- frontend/app.html: 新增健康检测UI界面

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/app.js

@@ -148,6 +148,15 @@ createApp({
         }
       },
 
+      // 健康检测
+      healthCheck: {
+        loading: false,
+        lastCheck: null,
+        overallStatus: null, // healthy, warning, critical
+        summary: { total: 0, pass: 0, warning: 0, fail: 0, info: 0 },
+        checks: []
+      },
+
       // Toast通知
       toasts: [],
       toastIdCounter: 0,
@@ -2041,10 +2050,11 @@ handleDragLeave(e) {
           this.loadShares();
           break;
         case 'admin':
-          // 切换到管理后台时，重新加载用户列表
+          // 切换到管理后台时，重新加载用户列表和健康检测
           if (this.user && this.user.is_admin) {
             this.loadUsers();
             this.loadServerStorageStats();
+            this.loadHealthCheck();
           }
           break;
         case 'settings':
@@ -2260,6 +2270,67 @@ handleDragLeave(e) {
       }
     },
 
+    // ===== 健康检测 =====
+
+    async loadHealthCheck() {
+      this.healthCheck.loading = true;
+      try {
+        const response = await axios.get(`${this.apiBase}/api/admin/health-check`, {
+          headers: { Authorization: `Bearer ${this.token}` }
+        });
+
+        if (response.data.success) {
+          this.healthCheck.overallStatus = response.data.overallStatus;
+          this.healthCheck.summary = response.data.summary;
+          this.healthCheck.checks = response.data.checks;
+          this.healthCheck.lastCheck = response.data.timestamp;
+        }
+      } catch (error) {
+        console.error('健康检测失败:', error);
+        this.showToast('error', '错误', '健康检测失败');
+      } finally {
+        this.healthCheck.loading = false;
+      }
+    },
+
+    getHealthStatusColor(status) {
+      const colors = {
+        pass: 'bg-green-100 text-green-800',
+        warning: 'bg-yellow-100 text-yellow-800',
+        fail: 'bg-red-100 text-red-800',
+        info: 'bg-blue-100 text-blue-800'
+      };
+      return colors[status] || 'bg-gray-100 text-gray-800';
+    },
+
+    getHealthStatusIcon(status) {
+      const icons = {
+        pass: '✓',
+        warning: '⚠',
+        fail: '✗',
+        info: 'ℹ'
+      };
+      return icons[status] || '?';
+    },
+
+    getOverallStatusColor(status) {
+      const colors = {
+        healthy: 'text-green-600',
+        warning: 'text-yellow-600',
+        critical: 'text-red-600'
+      };
+      return colors[status] || 'text-gray-600';
+    },
+
+    getOverallStatusText(status) {
+      const texts = {
+        healthy: '系统健康',
+        warning: '存在警告',
+        critical: '存在问题'
+      };
+      return texts[status] || '未知';
+    },
+
     // ===== 上传工具管理 =====
 
     // 检测上传工具是否存在