feat: 产品内知识库（obsidian-wiki 兼容 vault）

后端：新增自包含 deerflow.knowledge 模块（models/repository/schemas/
extractor/sources/markdown_vault/manifest/obsidian_adapter/exporter/
search/service），通过 deps.py 装配为 app.state.knowledge_service，
挂载 /api/knowledge 路由；config.yaml 增加 knowledge 配置段，
AppConfig 注册 KnowledgeConfig，ORM 注册 4 张 knowledge_* 表。

前端：新增知识库页面（KnowledgeBasePage/KnowledgeGraphPage）、
core/knowledge api/hooks/types、聊天侧 knowledge-save-trigger，
侧边栏增加「知识库」入口。

知识库为全局共享，不做 user_id 隔离，写入记录 created_by/updated_by
作为审计。

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

frontend-web/src/pages/KnowledgeGraphPage.tsx

@@ -0,0 +1,79 @@
+import { ArrowLeft, Loader2, RefreshCw } from "lucide-react";
+import { useCallback, useEffect, useState } from "react";
+import { useNavigate } from "react-router-dom";
+import { toast } from "sonner";
+
+import { Button } from "@/components/ui/button";
+import { knowledgeExportFileUrl } from "@/core/knowledge/api";
+import { useKnowledgeActions } from "@/core/knowledge/hooks";
+
+export default function KnowledgeGraphPage() {
+  const navigate = useNavigate();
+  const { exportGraph } = useKnowledgeActions();
+  const [src, setSrc] = useState<string | null>(null);
+  const [stats, setStats] = useState<{ nodes: number; edges: number } | null>(null);
+
+  const regenerate = useCallback(async () => {
+    try {
+      const result = await exportGraph.mutateAsync();
+      setStats(result.stats);
+      // Cache-bust the iframe so it reflects the freshly generated graph.
+      setSrc(`${knowledgeExportFileUrl("graph.html")}?t=${Date.now()}`);
+    } catch (error) {
+      toast.error(error instanceof Error ? error.message : "生成图谱失败");
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  useEffect(() => {
+    void regenerate();
+  }, [regenerate]);
+
+  return (
+    <div className="flex size-full min-h-0 flex-col">
+      <header className="flex items-center gap-2 border-b p-3">
+        <Button
+          variant="ghost"
+          size="sm"
+          onClick={() => navigate("/page/workspace/knowledge")}
+        >
+          <ArrowLeft className="size-4" /> 返回
+        </Button>
+        <h1 className="text-base font-semibold">知识图谱</h1>
+        {stats ? (
+          <span className="text-muted-foreground text-xs">
+            {stats.nodes} 个节点 · {stats.edges} 条关系
+          </span>
+        ) : null}
+        <Button
+          variant="outline"
+          size="sm"
+          className="ml-auto"
+          onClick={() => void regenerate()}
+          disabled={exportGraph.isPending}
+        >
+          {exportGraph.isPending ? (
+            <Loader2 className="size-4 animate-spin" />
+          ) : (
+            <RefreshCw className="size-4" />
+          )}
+          重新生成
+        </Button>
+      </header>
+      <div className="min-h-0 flex-1">
+        {src ? (
+          <iframe
+            src={src}
+            title="知识图谱"
+            className="size-full border-0"
+            sandbox="allow-scripts allow-same-origin"
+          />
+        ) : (
+          <div className="text-muted-foreground flex h-full items-center justify-center text-sm">
+            <Loader2 className="mr-2 size-4 animate-spin" /> 生成图谱中...
+          </div>
+        )}
+      </div>
+    </div>
+  );
+}