添加抓取失败网址记录功能

- 新增 failed_urls 数据库表存储失败URL
- 抓取失败时自动记录URL、标题、错误信息
- 搜索页面显示失败URL列表
- 支持重试单个/全部失败URL
- 支持删除和清空失败记录
- 显示重试次数和时间

static/css/search.css

@@ -351,4 +351,87 @@
         width: 100%;
         justify-content: space-between;
     }
+}
+
+/* 失败URL区域 */
+.failed-urls-section {
+    background: white;
+    border-radius: 12px;
+    box-shadow: 0 2px 4px rgba(0,0,0,0.05);
+    margin-top: 20px;
+}
+
+.failed-urls-section .panel-header {
+    background: #fef3c7;
+}
+
+.failed-urls-section .panel-header h2 {
+    color: #92400e;
+}
+
+.failed-count {
+    color: #92400e;
+    font-weight: bold;
+}
+
+.failed-urls-list {
+    display: flex;
+    flex-direction: column;
+    gap: 10px;
+}
+
+.failed-url-item {
+    display: flex;
+    justify-content: space-between;
+    align-items: flex-start;
+    padding: 15px;
+    border: 1px solid #fcd34d;
+    border-radius: 8px;
+    background: #fffbeb;
+}
+
+.failed-url-item.loading {
+    opacity: 0.5;
+}
+
+.failed-url-info {
+    flex: 1;
+}
+
+.failed-url-title {
+    font-weight: 500;
+    color: #333;
+    margin-bottom: 5px;
+}
+
+.failed-url-detail {
+    font-size: 13px;
+    margin-bottom: 5px;
+}
+
+.failed-url-detail a {
+    color: #3b82f6;
+    text-decoration: none;
+}
+
+.failed-url-detail a:hover {
+    text-decoration: underline;
+}
+
+.failed-error {
+    color: #dc2626;
+    margin-left: 10px;
+    font-size: 12px;
+}
+
+.failed-url-meta {
+    font-size: 12px;
+    color: #666;
+    display: flex;
+    gap: 15px;
+}
+
+.failed-url-actions {
+    display: flex;
+    gap: 8px;
 }