feat: improve app ui and project metadata

apps/web/app/settings/providers/page.tsx

@@ -1,5 +1,6 @@
 import { AppShell } from "@/components/AppShell";
 import { ProvidersSettings } from "@/components/settings/ProvidersSettings";
+import { PageHeader } from "@/components/ui/PageHeader";
 import { fetchKimiOauthStatus, fetchProviders } from "@/lib/api/server";
 import type { ProvidersResponse } from "@/lib/api/types";
 
@@ -27,7 +28,11 @@ export default async function ProvidersSettingsPage() {
 
   return (
     <AppShell title="设置 › 模型与提供商">
-      <div className="mx-auto max-w-3xl px-8 py-10">
+      <div className="mx-auto max-w-6xl px-4 py-8 sm:px-8 sm:py-10">
+        <PageHeader
+          title="模型与提供商"
+          description="配置写手、分析、轻量三类能力档位的路由，并管理 API Key 与 Kimi Code OAuth。"
+        />
         {loadError ? (
           <p className="rounded border border-conflict bg-panel p-6 text-conflict">
             无法连接后端服务，请确认 API 已启动后刷新。