Implement chat queue fallback

ai_knowledge_base_v2/apps/admin-web/src/App.vue

@@ -275,6 +275,33 @@ const systemSettingSections: SystemSettingSection[] = [
         defaultValue: true,
         description: "后台始终记录引用；此项控制用户端是否展示。",
       },
+      {
+        key: "chat_max_active_requests",
+        label: "问答最大并发数",
+        type: "number",
+        defaultValue: 2,
+        min: 1,
+        max: 1000,
+        description: "同一后端进程内同时进入飞书和模型生成链路的最大请求数。",
+      },
+      {
+        key: "chat_max_queue_size",
+        label: "问答最大排队数",
+        type: "number",
+        defaultValue: 20,
+        min: 0,
+        max: 10000,
+        description: "超过最大并发后允许等待的请求数量，超过后直接提示稍后再试。",
+      },
+      {
+        key: "chat_queue_timeout_seconds",
+        label: "问答排队超时（秒）",
+        type: "number",
+        defaultValue: 60,
+        min: 1,
+        max: 3600,
+        description: "请求在排队中超过该时间后自动结束并提示用户稍后再试。",
+      },
     ],
   },
   {