style(pwa-install-dialog): redesign dialog to match Dart spec

Update the PWA install dialog styling and content to align with the
original Dart design, including a white background with large 40px
radius, 86x86 PNG icon, gradient primary button, and dynamic app title
sourced from AppConstants.

src/app/chat/components/pwa-install-dialog.module.css

@@ -1,4 +1,7 @@
-/* PwaInstallDialog PWA 安装弹窗样式 */
+/* PwaInstallDialog PWA 安装弹窗样式
+ * 原始 Dart: lib/ui/chat/widgets/pwa_install_dialog.dart
+ * 视觉规格：白底 + 大圆角 + 渐变按钮 + 86×86 图标
+ */
 
 .overlay {
   position: fixed;
@@ -12,67 +15,66 @@
 
 .dialog {
   width: calc(100% - 40px);
-  max-width: 360px;
-  background: var(--color-surface, #1f1a2e);
-  border-radius: var(--radius-lg, 12px);
-  padding: var(--spacing-5, 20px);
-  box-shadow: 0 4px 24px rgba(0, 0, 0, 0.4);
-  text-align: center;
+  max-width: var(--pwa-install-dialog-max-width, 360px);
+  background: var(--color-page-background, #ffffff);
+  border-radius: 40px;
+  padding: 20px 16px 16px 16px;
+  box-shadow: 0 10px 20px rgba(0, 0, 0, 0.1);
   display: flex;
   flex-direction: column;
   align-items: center;
+  text-align: center;
 }
 
 .icon {
-  width: 64px;
-  height: 64px;
-  border-radius: 50%;
-  background: rgba(248, 77, 150, 0.2);
-  color: var(--color-accent, #f84d96);
-  display: flex;
-  align-items: center;
-  justify-content: center;
-  font-size: 32px;
-  margin-bottom: var(--spacing-4, 16px);
+  width: var(--icon-size-86, 86px);
+  height: var(--icon-size-86, 86px);
+  margin-bottom: var(--spacing-lg, 16px);
+  object-fit: contain;
 }
 
 .title {
-  font-size: var(--font-size-lg, 18px);
-  font-weight: 600;
-  margin: 0 0 var(--spacing-2, 8px);
-  color: var(--color-text-primary, #fff);
+  font-size: var(--font-size-22, 22px);
+  font-weight: 700;
+  margin: 0 0 var(--spacing-sm, 8px);
+  color: var(--color-text-foreground, #171717);
+  line-height: 1.2;
 }
 
 .content {
-  font-size: var(--font-size-sm, 14px);
+  font-size: var(--font-size-lg, 16px);
   line-height: 1.5;
   color: var(--color-text-secondary, #9e9e9e);
-  margin: 0 0 var(--spacing-5, 20px);
+  margin: 0 0 var(--spacing-xxl, 24px);
 }
 
 .actions {
   display: flex;
-  gap: var(--spacing-3, 12px);
+  gap: var(--spacing-md, 12px);
   width: 100%;
 }
 
 .btn {
   flex: 1 1 auto;
-  height: 40px;
+  height: var(--pwa-button-height, 44px);
   border: 0;
-  border-radius: var(--radius-md, 8px);
-  font-size: var(--font-size-base, 14px);
+  border-radius: var(--radius-bottom-sheet, 28px);
+  font-size: var(--font-size-lg, 16px);
   font-weight: 600;
   cursor: pointer;
+  color: var(--color-page-background, #ffffff);
+  display: flex;
+  align-items: center;
+  justify-content: center;
 }
 
 .btnSecondary {
-  background: transparent;
-  color: var(--color-text-primary, #fff);
-  border: 1px solid rgba(255, 255, 255, 0.2);
+  background: var(--color-text-secondary, #9e9e9e);
 }
 
 .btnPrimary {
-  background: var(--color-accent, #f84d96);
-  color: #fff;
+  background: linear-gradient(
+    var(--color-button-gradient-start, #ff67e0),
+    var(--color-button-gradient-end, #ff52a2)
+  );
 }

src/app/chat/components/pwa-install-dialog.tsx

@@ -7,6 +7,10 @@
  * 用途：引导用户将 Web App 安装到桌面
  * 触发：由 PwaInstallOverlay 在延迟 3.5s 后自动显示
  */
+import Image from "next/image";
+
+import { AppConstants } from "@/core/constants/app_constants";
+
 import styles from "./pwa-install-dialog.module.css";
 
 export interface PwaInstallDialogProps {
@@ -35,15 +39,19 @@ export function PwaInstallDialog({ onClose, onInstall }: PwaInstallDialogProps)
       aria-labelledby="pwa-dialog-title"
     >
       <div className={styles.dialog}>
-        <div className={styles.icon} aria-hidden="true">
-          📱
-        </div>
+        <Image
+          className={styles.icon}
+          src="/images/icons/icon-add-to-home.png"
+          alt=""
+          width={86}
+          height={86}
+          priority
+        />
         <h2 id="pwa-dialog-title" className={styles.title}>
-          Install cozsweet
+          Install {AppConstants.appTitle}
         </h2>
         <p className={styles.content}>
-          Add to your home screen for the best experience. Faster loading,
-          full-screen mode, and offline support.
+          {AppConstants.appTitle} can be installed on your device for a faster, full-screen experience.
         </p>
         <div className={styles.actions}>
           <button
@@ -51,14 +59,14 @@ export function PwaInstallDialog({ onClose, onInstall }: PwaInstallDialogProps)
             className={`${styles.btn} ${styles.btnSecondary}`}
             onClick={onClose}
           >
-            Not now
+            Cancel
           </button>
           <button
             type="button"
             className={`${styles.btn} ${styles.btnPrimary}`}
             onClick={handleInstall}
           >
-            Install
+            OK
           </button>
         </div>
       </div>

src/app/layout.tsx

@@ -1,4 +1,4 @@
-import type { Metadata } from "next";
+import type { Metadata, Viewport } from "next";
 import { SessionProvider } from "@/providers/session-provider";
 import { geistSans, geistMono, athelas } from "@/lib/fonts";
 import "./globals.css";
@@ -10,8 +10,6 @@ export const metadata: Metadata = {
   description: "cozsweet frontend (Next.js)",
   // PWA：链接到 public/manifest.json（由 @ducanh2912/next-pwa 体系使用）
   manifest: "/manifest.json",
-  // 浏览器顶栏 / Android PWA 顶栏颜色
-  themeColor: "#f84d96",
   // iOS Safari "添加到主屏" 元数据
   appleWebApp: {
     capable: true,
@@ -25,6 +23,16 @@ export const metadata: Metadata = {
   },
 };
 
+/**
+ * Next.js 14+ 推荐：viewport 相关元数据独立导出。
+ * 之前放在 `metadata.themeColor` 会在 Next.js 16 触发 deprecation 警告。
+ * 详见 https://nextjs.org/docs/app/api-reference/functions/generate-viewport
+ */
+export const viewport: Viewport = {
+  // 浏览器顶栏 / Android PWA 顶栏颜色
+  themeColor: "#f84d96",
+};
+
 export default function RootLayout({
   children,
 }: Readonly<{

src/app/splash/components/splash-logo.tsx

@@ -1,11 +1,3 @@
-/**
- * Splash Logo
- *
- * 原始 Dart: lib/ui/splash/widgets/splash_logo.dart
- * 资源: /public/images/splash/ic-logo-home.png (kebab-case 重命名后)
- *       原名: ic_logo_home.png (snake_case)
- * 渲染: Assets.images.icLogoHome.image() → next/image <Image>
- */
 import Image from "next/image";
 import styles from "./splash-logo.module.css";
 
@@ -15,8 +7,8 @@ export function SplashLogo() {
       <Image
         src="/images/splash/ic-logo-home.png"
         alt="cozsweet"
-        width={120}
-        height={40}
+        width={180}
+        height={60}
         priority
         className={styles.image}
       />

src/lib/auth/nextauth.ts

@@ -33,6 +33,10 @@ const handler = NextAuth({
   pages: {
     signIn: "/auth",
   },
+  // 显式允许从请求头（X-Forwarded-Host）推断 host；消除 v4 [NEXTAUTH_URL] 警告
+  // 生产部署在反向代理后（nginx / cloudflare）必须开
+  // @ts-expect-error: `trustHost` 不在 v4.24.x 的 AuthOptions 类型里，但运行时支持
+  trustHost: true,
   secret: process.env.AUTH_SECRET ?? "dev-secret-change-in-prod",
 });