feat: 可配置站点 URL 风格

- 新增 urlStyle 工具与测试：postPath/userPath/sitePagePath 统一生成链接
- 管理端新增 UrlStylePanel 设置面板，settings 服务与 handler 适配
- 全站路由链接与 JSON-LD/sitemap 切换为统一 URL 生成
- middleware 与相关组件适配

frontend/components/MarkdownEditor.tsx

@@ -40,6 +40,8 @@ import ImageInsertModal from "@/components/ImageInsertModal";
 import TimelineEditor from "@/components/TimelineEditor";
 import { resolveTimelineBlockForEdit } from "@/lib/directiveBlocks";
 import { SHIKI_LANG_IDS } from "@/components/markdown/shikiHighlighter";
+import { postPath } from "@/lib/urlStyle";
+import { useUrlStyle } from "@/components/SiteBrandProvider";
 
 type MarkdownEditorProps = {
   value: string;
@@ -157,6 +159,7 @@ export default function MarkdownEditor({
   onUploadingChange,
 }: MarkdownEditorProps) {
   const taRef = useRef<HTMLTextAreaElement>(null);
+  const urlStyle = useUrlStyle();
   const fileRef = useRef<HTMLInputElement>(null);
   const toolbarRef = useRef<HTMLDivElement>(null);
   const [mode, setMode] = useState<EditorMode>("write");
@@ -472,7 +475,7 @@ export default function MarkdownEditor({
 
   /** 选中站内帖子：回填 URL 与文字，用户可再编辑后点「插入」 */
   const pickPostLink = (p: PostListItem) => {
-    setLinkUrl(`/post/${p.id}`);
+    setLinkUrl(postPath(urlStyle, p.id));
     setLinkText(p.title);
   };