feat: 全面重构网站工程化体系与 UI 架构

- 将单体 style.css 拆分为 tokens/reset/fonts/layout/responsive/组件级 CSS 模块
- 从 Google Fonts CDN 迁移至本地自托管字体（JetBrainsMono、NotoSansSC）
- 引入 Vitest + Testing Library 测试体系，新增单元测试
- 添加 GitHub Actions CI 流水线（lint → build → test）
- 新增 Prettier 格式化与 ESLint 规则强化
- 重构全部 YAML 数据文件，完善项目详情页（截图轮播、更新日志）
- 新增项目文档编写指南（docs/create-project.md）

src/components/Nav.tsx

@@ -5,7 +5,8 @@ import { useI18n } from '../hooks/useI18n';
 import { siteData } from '../data/siteData';
 
 export default function Nav() {
-  const { theme, mobileMenuOpen, toggleTheme, toggleLang, openMobileMenu, closeMobileMenu } = useApp();
+  const { theme, mobileMenuOpen, toggleTheme, toggleLang, openMobileMenu, closeMobileMenu } =
+    useApp();
   const { t, bi } = useI18n();
   const location = useLocation();
   const currentPath = '/' + location.pathname.slice(1);
@@ -15,14 +16,17 @@ export default function Nav() {
       <nav className="nav">
         <div className="nav-inner">
           <Link to="/" className="nav-brand">
-            <span className="nav-brand-icon">Z</span>
+            {siteData.brand.logo ? (
+              <img src={siteData.brand.logo} alt={bi(siteData.brand.name)} className="nav-brand-icon" />
+            ) : (
+              <span className="nav-brand-icon">Z</span>
+            )}
             {bi(siteData.brand.name)}
           </Link>
           <div className="nav-links">
-            {siteData.nav.map(n => {
+            {siteData.nav.map((n) => {
               const navPath = n.hash.slice(2) || '/';
-              const isActive = currentPath === navPath ||
-                (navPath === '/' && currentPath === '');
+              const isActive = currentPath === navPath || (navPath === '/' && currentPath === '');
               return (
                 <Link
                   key={n.id}
@@ -56,7 +60,7 @@ export default function Nav() {
         </div>
       </nav>
       <div className={`nav-mobile-menu${mobileMenuOpen ? ' open' : ''}`}>
-        {siteData.nav.map(n => {
+        {siteData.nav.map((n) => {
           const navPath = n.hash.slice(2) || '/';
           return (
             <Link