feat: add legal tabs and update header assets

Switch the legal page to tabbed EULA/privacy content with URL sync, update header styling, and migrate footer icons to Ant Design.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/page/legal/index.tsx

@@ -0,0 +1,34 @@
+import { Tabs } from "antd"
+import { useSearchParams } from "react-router-dom"
+import MarkdownRenderer from "@/components/markdown-renderer"
+import { html as EulaHtml } from "@/docs/EULA.md"
+import { html as PrivacyHtml } from "@/docs/PrivacyPolicy.md"
+
+const tabKeys = new Set(["eula", "privacy"])
+
+export default function LegalPage() {
+  const [searchParams, setSearchParams] = useSearchParams()
+  const rawTab = searchParams.get("tab")
+  const activeTab = rawTab && tabKeys.has(rawTab) ? rawTab : "eula"
+
+  return (
+    <div className="mx-auto max-w-4xl">
+      <Tabs
+        activeKey={activeTab}
+        onChange={(key) => setSearchParams({ tab: key })}
+        items={[
+          {
+            key: "eula",
+            label: "最终用户许可协议",
+            children: <MarkdownRenderer html={EulaHtml} />,
+          },
+          {
+            key: "privacy",
+            label: "隐私政策",
+            children: <MarkdownRenderer html={PrivacyHtml} />,
+          },
+        ]}
+      />
+    </div>
+  )
+}