feat(fonts): 字体三轨预分片自托管接入

- lxgw-wenkai-screen-webfont + @fontsource/noto-sans-sc(400/500/700)
  + @fontsource/jetbrains-mono(400/700)，均 OFL
- unicode-range 按需加载 + font-display swap；家族名与 tokens 栈首一致
- 教训：包 css 不能经 .css 文件 ESM import，须组件 frontmatter 持有

验证: pnpm astro build exit 0；dist woff2 分片 399 个（>50 门槛）

Spec: 2026-10-24_add-blog-skeleton
Co-authored-by: GLM-5.3

package.json

@@ -10,6 +10,9 @@
     "astro": "astro"
   },
   "dependencies": {
-    "astro": "^7.3.8"
+    "@fontsource/jetbrains-mono": "^5.3.0",
+    "@fontsource/noto-sans-sc": "^5.3.1",
+    "astro": "^7.3.8",
+    "lxgw-wenkai-screen-webfont": "^1.7.0"
   }
 }