新增操作引导步骤及相关配图；调整全局文字颜色变量

src/app/admin/(dashboard)/page.tsx

@@ -43,6 +43,7 @@ export default async function DashboardPage(props: DashboardPageProps) {
           </div>
         </CardContent>
       </Card>
+
       {/* 长效 */}
       <Card className={`col-start-2 row-start-2`}>
         <CardHeader>