feat: dist-site 多主题模板 + 中英双语 i18n

- 新增 4 套主题模板：starter/default/dark/minimal
  - Starter: 毛玻璃 + GradientText + SpotlightCard (原有风格)
  - Default: Aurora 极光背景 + SplitText + TiltedCard
  - Dark: Particles 粒子 + DecryptedText 赛博朋克风格
  - Minimal: 极简优雅 + FadeContent 淡入动画
- 新增 i18n 中英双语支持 (i18next + browser-languagedetector)
- 新增 ThemeProvider 运行时主题切换 (根据 theme_template 字段)
- 新增 11 个 react-bits 动画组件
- 所有页面文案国际化 (Login/Register/Dashboard/Tokens/Pricing/Packages)
- 新增 README.md + README.zh.md 含主题切换指南

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/App.jsx

@@ -1,9 +1,8 @@
 import React, { lazy, Suspense } from 'react';
 import { Routes, Route, Navigate } from 'react-router-dom';
-import Layout from './components/Layout';
 import AuthGuard from './components/AuthGuard';
+import { ThemeProvider, useTheme } from './context/ThemeContext';
 
-const Home = lazy(() => import('./pages/Home'));
 const Login = lazy(() => import('./pages/Login'));
 const Register = lazy(() => import('./pages/Register'));
 const Dashboard = lazy(() => import('./pages/Dashboard'));
@@ -17,11 +16,13 @@ const Loading = () => (
   </div>
 );
 
-export default function App() {
+function ThemedRoutes() {
+  const { Home, Layout } = useTheme();
+
   return (
     <Suspense fallback={<Loading />}>
       <Routes>
-        {/* Public pages with layout */}
+        {/* Public pages with themed layout */}
         <Route element={<Layout />}>
           <Route path="/" element={<Home />} />
           <Route path="/pricing" element={<Pricing />} />
@@ -41,3 +42,11 @@ export default function App() {
     </Suspense>
   );
 }
+
+export default function App() {
+  return (
+    <ThemeProvider>
+      <ThemedRoutes />
+    </ThemeProvider>
+  );
+}