fix: 优化分站 API Key 页面显示细节

- 移除空状态冗余创建按钮，改为提示点击上方卡片
- 移除 My API Keys 标题栏多余的新建按钮
- ConfigExporter 无 key 时提示改为"请先创建 API Key"
- 修复 KeyGroupCard 推荐/折扣标签颜色适配所有主题

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

src/components/ConfigExporter.jsx

@@ -247,8 +247,8 @@ print(message.content[0].text)`;
         <svg className="w-8 h-8 mx-auto mb-3 text-page-muted" fill="none" viewBox="0 0 24 24" stroke="currentColor">
           <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={1.5} d="M15 7a2 2 0 012 2m4 0a6 6 0 01-7.743 5.743L11 17H9v2H7v2H4a1 1 0 01-1-1v-2.586a1 1 0 01.293-.707l5.964-5.964A6 6 0 1121 9z" />
         </svg>
-        <p className="text-sm text-page-secondary mb-1">{t('config.loginPrompt')}</p>
-        <p className="text-xs text-page-muted">{t('config.loginDesc')}</p>
+        <p className="text-sm text-page-secondary mb-1">{t('config.noKeyPrompt')}</p>
+        <p className="text-xs text-page-muted">{t('config.noKeyDesc')}</p>
       </div>
     );
   }