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/core/threads/hooks.ts

@@ -664,6 +664,9 @@ export function useThreadStream({
           lockThreadRagMode(threadId);
         }
 
+        const contextCompressionEnabled =
+          localSettings.display.contextCompressionEnabled ?? false;
+
         const mergedContext = {
           ...context,
           ...extraContext,
@@ -715,6 +718,7 @@ export function useThreadStream({
               memory_injection_enabled:
                 mergedContext.memory_injection_enabled ?? true,
               rag_mode_enabled: ragModeEnabled,
+              summarization_enabled: contextCompressionEnabled,
               thread_id: threadId,
             },
           },