feat(web): use history routing and preserve scroll on filter changes

reaction_board/web/server.py

@@ -388,7 +388,12 @@ border-color:#3a2c22;color:#f3e9dc}button{background:#e9b97c;color:#2a1a10}}
             except ValueError:
                 raise ApiError(HTTPStatus.NOT_FOUND, "not_found", "文件不存在")
         else:
-            raise ApiError(HTTPStatus.NOT_FOUND, "not_found", "页面不存在")
+            # 伪静态前端路由：/rank、/video/123、/up/123 等直接返回 index.html，
+            # 由前端根据 location.pathname 渲染。带扩展名的路径仍按文件处理并返回 404。
+            last_segment = path.rstrip("/").rsplit("/", 1)[-1]
+            if "." in last_segment:
+                raise ApiError(HTTPStatus.NOT_FOUND, "not_found", "文件不存在")
+            target = STATIC_ROOT / "index.html"
         if not target.is_file():
             raise ApiError(HTTPStatus.NOT_FOUND, "not_found", "页面不存在")
         content_type = mimetypes.guess_type(str(target))[0] or "application/octet-stream"