feat: 知识批量沉淀改为后台任务,避免 nginx 504

- /ingest/threads/batch 新增 background 参数(默认 true),立即返回 {queued:true}
- 抽取循环抽出 _run_batch_ingest,后台路径显式传入 created_by
- 前端知识库页与输入框、线程 hooks/types 配套调整
- config.yaml 上下文压缩测试值

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend-web/src/pages/KnowledgeBasePage.tsx

@@ -176,10 +176,21 @@ function BatchImportDialog({
         skip_existing: skipExisting,
         status: "approved",
         include_sources: true,
+        // Run in the background so the request returns immediately — a large
+        // batch otherwise blocks past the gateway timeout and shows "request
+        // failed". Threads stream into the list as they finish.
+        background: true,
         model_name: model,
         template_id: template,
         folder,
       });
+      if (result.queued) {
+        toast.success(
+          `已转入后台导入 ${result.processed} 个线程，完成后会陆续出现在左侧列表（可稍后刷新查看）`,
+        );
+        onOpenChange(false);
+        return;
+      }
       const base = `批量导入完成：新增 ${result.created}，跳过 ${result.skipped}，失败 ${result.failed}`;
       if (result.llm_fallback && result.llm_fallback > 0) {
         // The model failed on some threads — they were saved via rule-based
@@ -549,7 +560,7 @@ export default function KnowledgeBasePage() {
       keyword: debouncedKeyword || undefined,
       source_type: sourceType === "all" ? undefined : sourceType,
       status: status === "all" ? undefined : status,
-      limit: 500,
+      limit: 1000,
     }),
     [debouncedKeyword, sourceType, status],
   );