refactor(auth): centralize auth routing via proxy and marker cookie

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

@@ -17,10 +17,10 @@ import Link from "next/link";
 import { useRouter } from "next/navigation";
 import { useEffect, useRef } from "react";
 
-import { useAuthState, useAuthDispatch } from "@/stores/auth/auth-context";
+import { useAuthState } from "@/stores/auth/auth-context";
 import { useChatDispatch } from "@/stores/chat/chat-context";
 import { useUserDispatch } from "@/stores/user/user-context";
-import { facebookLogin, useAuthGate } from "@/lib/auth/nextauth";
+import { facebookLogin } from "@/lib/auth/nextauth";
 import { ROUTES } from "@/router/routes";
 import { LoadingIndicator } from "@/app/_components/core/loading-indicator";
 import styles from "./splash-button.module.css";
@@ -31,10 +31,13 @@ export interface SplashButtonProps {
 }
 
 export function SplashButton({ skipHref = ROUTES.chat }: SplashButtonProps) {
-  // ===== 鉴权状态 =====
-  const { isAuthed } = useAuthGate();
+  // ===== 鉴权路由跳转已由 src/router/proxy.ts 集中处理 =====
+  // 本组件只负责：
+  //   1. 触发登录动作
+  //   2. 登录成功后初始化 chat/user store + navigate 到 /chat（业务层动作，
+  //      不是鉴权判断；proxy 会让通过因为 cookie 已设）
+
   const state = useAuthState();
-  const authDispatch = useAuthDispatch();
   const isLoading = state.isLoading;
 
   // ===== 跨 store 初始化（登录成功后触发） =====
@@ -43,11 +46,6 @@ export function SplashButton({ skipHref = ROUTES.chat }: SplashButtonProps) {
   const router = useRouter();
   const wasSuccess = useRef(false);
 
-  // 已登录时跳 /chat
-  useEffect(() => {
-    if (isAuthed) router.replace(ROUTES.chat);
-  }, [isAuthed, router]);
-
   // 邮箱登录成功跳 /chat + 通知 chat/user 初始化
   useEffect(() => {
     if (state.isSuccess && !wasSuccess.current) {