feat: 剩余页面 useT() 改造 + 首页课程动态加载

- 搜索/发现/工具/My 页面全部使用 useT()，支持中英切换
- 搜索页 Badge variant 修正
- 首页热门专题改为从 API 动态获取（无数据时用静态兜底）
- 新增 discover 翻译键 viewCount/likeCount/postStats
- 首页/仪表盘/社区 等 JSX 优化

frontend/src/app/page.tsx

@@ -1,12 +1,22 @@
 'use client';
 
 import Link from 'next/link';
+import { useState, useEffect } from 'react';
 import { HomePageClient } from './home-client';
 import { ArrowRight, Sparkles, BookOpen, Bot, Compass, Zap } from 'lucide-react';
 import { useT } from '@/i18n';
+import { API_BASE } from '@/lib/config';
 
 export default function HomePage() {
   const t = useT();
+  const [courses, setCourses] = useState<any[]>([]);
+
+  useEffect(() => {
+    fetch(`${API_BASE}/courses?pageSize=3`)
+      .then(r => r.json()).then(data => setCourses(data.items || []))
+      .catch(() => {});
+  }, []);
+
   const stats = [
     { value: '50+', label: t.home.statTopics },
     { value: '200+', label: t.home.statPrompts },
@@ -107,25 +117,35 @@ export default function HomePage() {
             </Link>
           </div>
           <div className="grid grid-cols-1 md:grid-cols-3 gap-6">
-            {[
-              { title: 'AI 通识：零基础入门', students: '1,280', tag: t.courses.free, gradient: 'from-brand-500 to-blue-500', desc: '面向零基础用户，带你了解 AI 的基本概念、发展历程和实际应用。' },
-              { title: '提示词工程从入门到精通', students: '860', tag: '热门', gradient: 'from-violet-500 to-purple-500', desc: '系统学习提示词编写技巧，掌握与 AI 高效沟通的方法。' },
-              { title: '用 AI 提升 10 倍办公效率', students: '2,150', tag: '推荐', gradient: 'from-amber-500 to-orange-500', desc: '学习使用 AI 工具处理文档、数据分析、演示制作等日常工作。' },
-            ].map((course) => (
-              <div key={course.title} className="group bg-card rounded-xl border border-border overflow-hidden hover:shadow-xl transition-all hover:-translate-y-1">
-                <div className={`h-2 bg-gradient-to-r ${course.gradient}`} />
-                <div className="p-6">
-                  <div className="flex items-center justify-between mb-3">
-                    <span className="text-xs font-medium text-brand-700 dark:text-brand-300 bg-brand-50 dark:bg-brand-900/30 px-2 py-1 rounded-full">{course.tag}</span>
-                  </div>
-                  <h3 className="text-lg font-semibold mb-2 group-hover:text-brand-600 transition-colors">{course.title}</h3>
-                  <p className="text-sm text-muted-foreground mb-4 line-clamp-2">{course.desc}</p>
-                  <div className="flex items-center gap-4 text-sm text-muted-foreground">
-                    <span className="flex items-center gap-1"><BookOpen className="w-4 h-4" />{t.home.moduleCount.replace('{n}', course.students)}</span>
+            {courses.length > 0 ? courses.map((course: any) => (
+              <Link key={course.id} href={`/courses/${course.id}`} className="block group">
+                <div className="group bg-card rounded-xl border border-border overflow-hidden hover:shadow-xl transition-all hover:-translate-y-1">
+                  <div className="h-2 bg-gradient-to-r from-brand-500 to-blue-500" />
+                  <div className="p-6">
+                    <div className="flex items-center justify-between mb-3">
+                      <span className="text-xs font-medium text-brand-700 dark:text-brand-300 bg-brand-50 dark:bg-brand-900/30 px-2 py-1 rounded-full">{course.isFree ? t.courses.free : t.courses.paid}</span>
+                    </div>
+                    <h3 className="text-lg font-semibold mb-2 group-hover:text-brand-600 transition-colors">{course.title}</h3>
+                    <p className="text-sm text-muted-foreground mb-4 line-clamp-2">{course.description || ''}</p>
                   </div>
                 </div>
-              </div>
-            ))}
+              </Link>
+            )) : (
+              <>
+                {[{ title: 'AI 通识：零基础入门', tag: t.courses.free }, { title: '提示词工程从入门到精通', tag: '热门' }, { title: '用 AI 提升 10 倍办公效率', tag: '推荐' }].map((course) => (
+                  <div key={course.title} className="group bg-card rounded-xl border border-border overflow-hidden hover:shadow-xl transition-all hover:-translate-y-1">
+                    <div className="h-2 bg-gradient-to-r from-brand-500 to-blue-500" />
+                    <div className="p-6">
+                      <div className="flex items-center justify-between mb-3">
+                        <span className="text-xs font-medium text-brand-700 dark:text-brand-300 bg-brand-50 dark:bg-brand-900/30 px-2 py-1 rounded-full">{course.tag}</span>
+                      </div>
+                      <h3 className="text-lg font-semibold mb-2 group-hover:text-brand-600 transition-colors">{course.title}</h3>
+                      <p className="text-sm text-muted-foreground mb-4 line-clamp-2">探索 AI 世界</p>
+                    </div>
+                  </div>
+                ))}
+              </>
+            )}
           </div>
         </div>
       </section>