polish(frontend): 修正中文字重发虚，并疏朗首页与数据区

补齐 Noto 600/800 并关闭伪粗；Header 加大加粗导航并加板块入口；去掉灰块底、加大列表行距，站点数据格居中缩小数字。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/app/layout.tsx

@@ -24,7 +24,8 @@ const jakarta = Plus_Jakarta_Sans({
 });
 
 const notoSC = Noto_Sans_SC({
-  weight: ["400", "500", "700", "900"],
+  // 须覆盖站内实际用到的字重：缺档时浏览器会伪粗（synthetic bold），中文在 2K 屏发虚发糊
+  weight: ["400", "500", "600", "700", "800", "900"],
   variable: "--font-noto-sc",
   display: "swap",
 });