fix(auth): stabilize hydration-dependent UI

src/app/splash/hooks/use-splash-latest-message.ts

@@ -1,8 +1,9 @@
 "use client";
 
-import { useEffect, useState, useSyncExternalStore } from "react";
+import { useEffect, useState } from "react";
 
 import type { LoginStatus } from "@/data/dto/auth";
+import { useHasHydrated } from "@/hooks/use-has-hydrated";
 import { loadSplashLatestMessagePreview } from "@/lib/chat/splash_latest_message";
 import { useSplashLatestMessageCache } from "@/providers/splash-latest-message-provider";
 import { Logger, Result } from "@/utils";
@@ -26,21 +27,13 @@ interface SplashLatestMessageState {
   message: string | null;
 }
 
-const subscribeToHydration = () => () => undefined;
-const getClientHydrationSnapshot = () => true;
-const getServerHydrationSnapshot = () => false;
-
 export function useSplashLatestMessage({
   hasInitialized,
   isAuthLoading,
   loginStatus,
 }: UseSplashLatestMessageInput): UseSplashLatestMessageOutput {
   const cache = useSplashLatestMessageCache();
-  const hasHydrated = useSyncExternalStore(
-    subscribeToHydration,
-    getClientHydrationSnapshot,
-    getServerHydrationSnapshot,
-  );
+  const hasHydrated = useHasHydrated();
   const [state, setState] = useState<SplashLatestMessageState>({
     key: "",
     loaded: false,