feat: 剩余页面 useT() + 页脚 SystemConfig 动态渲染

- 学习分析/学习路径/设置/收藏/提示词工坊 页面 useT()
- 页脚联系邮箱/ICP备案号从 GET /public/config 动态获取
- 翻译键补齐: discover.viewCount/likeCount/postStats

frontend/src/components/layout/footer.tsx

@@ -1,8 +1,20 @@
+'use client';
+
+import { useEffect, useState } from 'react';
 import Link from 'next/link';
 import { useT } from '@/i18n';
+import { API_BASE } from '@/lib/config';
 
 export function Footer() {
   const t = useT();
+  const [config, setConfig] = useState<Record<string, string>>({});
+
+  useEffect(() => {
+    fetch(`${API_BASE}/public/config`)
+      .then(r => r.json()).then(data => setConfig(data || {}))
+      .catch(() => {});
+  }, []);
+
   return (
     <footer className="border-t border-border bg-muted/30">
       <div className="max-w-7xl mx-auto px-4 sm:px-6 lg:px-8 py-12 md:py-16">
@@ -33,7 +45,7 @@ export function Footer() {
           <div>
             <h4 className="text-sm font-semibold mb-3">{t.footer.contact}</h4>
             <ul className="space-y-2.5">
-              <li className="text-sm text-muted-foreground">邮箱：contact@yuzhiran.com</li>
+              <li className="text-sm text-muted-foreground">{config.contact_email ? `邮箱：${config.contact_email}` : '邮箱：contact@yuzhiran.com'}</li>
               <li className="text-sm text-muted-foreground">北京宇之然科技中心</li>
             </ul>
           </div>
@@ -43,11 +55,7 @@ export function Footer() {
             <p>{t.footer.copyright.replace('{year}', String(new Date().getFullYear()))}</p>
             <p>
               <a href="https://beian.miit.gov.cn/" target="_blank" rel="noopener noreferrer" className="hover:text-foreground transition-colors">
-                ICP 备案号：京ICP备XXXXXXXX号
-              </a>
-              <span className="mx-2">|</span>
-              <a href="https://www.beian.gov.cn/" target="_blank" rel="noopener noreferrer" className="hover:text-foreground transition-colors">
-                京公网安备 XXXXXXXXXXXX号
+                {config.icp_number ? `ICP 备案号：${config.icp_number}` : 'ICP 备案号：京ICP备XXXXXXXX号'}
               </a>
             </p>
           </div>