feat(AuthProvider): 添加认证状态管理和加载界面

重构认证逻辑为独立函数并添加状态管理，在认证过程中显示加载界面。同时添加主题切换按钮到加载界面。

src/components/AuthProvider.tsx

@@ -1,7 +1,11 @@
 'use client';
 
 import { usePathname, useRouter } from 'next/navigation';
-import { useEffect } from 'react';
+import { useCallback, useEffect, useState } from 'react';
+
+import { ThemeToggle } from '@/components/ThemeToggle';
+
+import { useSite } from './SiteProvider';
 
 interface Props {
   children: React.ReactNode;
@@ -10,37 +14,73 @@ interface Props {
 export default function AuthProvider({ children }: Props) {
   const router = useRouter();
   const pathname = usePathname();
+  const [isAuthenticated, setIsAuthenticated] = useState<boolean | null>(null);
+  const { siteName } = useSite();
+  const authenticate = useCallback(async () => {
+    // 登录页
+    if (pathname.startsWith('/login') || pathname.startsWith('/api/login')) {
+      setIsAuthenticated(true);
+      return;
+    }
 
-  useEffect(() => {
-    // 登录页或 API 路径不做校验，避免死循环
-    if (pathname.startsWith('/login')) return;
-
+    // 从localStorage获取密码
     const password = localStorage.getItem('password');
     const fullPath =
       typeof window !== 'undefined'
         ? window.location.pathname + window.location.search
         : pathname;
 
-    // 有密码时验证
-    (async () => {
-      try {
-        const res = await fetch('/api/login', {
-          method: 'POST',
-          headers: { 'Content-Type': 'application/json' },
-          body: JSON.stringify({ password }),
-        });
+    // 没有密码直接跳转
+    if (!password) {
+      router.replace(`/login?redirect=${encodeURIComponent(fullPath)}`);
+      setIsAuthenticated(false);
+      return;
+    }
 
-        if (!res.ok) {
-          // 校验未通过，清理并跳转登录
-          localStorage.removeItem('password');
-          router.replace(`/login?redirect=${encodeURIComponent(fullPath)}`);
-        }
-      } catch (error) {
-        // 网络错误等也认为未登录
-        router.replace(`/login?redirect=${encodeURIComponent(fullPath)}`);
-      }
-    })();
+    // 尝试认证
+    try {
+      const res = await fetch('/api/login', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ password }),
+      });
+
+      if (!res.ok) throw new Error('认证失败');
+
+      setIsAuthenticated(true);
+    } catch (error) {
+      // 认证失败，清理并跳转登录
+      setIsAuthenticated(false);
+      localStorage.removeItem('password');
+      router.replace(`/login?redirect=${encodeURIComponent(fullPath)}`);
+    }
   }, [pathname, router]);
 
-  return <>{children}</>;
+  useEffect(() => {
+    authenticate();
+  }, [pathname, authenticate]);
+
+  // 认证状态未知时显示加载状态
+  if (!isAuthenticated) {
+    return (
+      <div className='relative min-h-screen flex items-center justify-center px-4 overflow-hidden'>
+        <div className='absolute top-4 right-4'>
+          <ThemeToggle />
+        </div>
+        <div className='relative z-10 w-full max-w-md rounded-3xl bg-gradient-to-b from-white/90 via-white/70 to-white/40 dark:from-zinc-900/90 dark:via-zinc-900/70 dark:to-zinc-900/40 backdrop-blur-xl shadow-2xl p-10 dark:border dark:border-zinc-800'>
+          <h1 className='text-green-600 tracking-tight text-center text-3xl font-extrabold mb-8 bg-clip-text drop-shadow-sm'>
+            {siteName}
+          </h1>
+          <div className='flex justify-center my-10'>
+            <div className='animate-spin rounded-full h-16 w-16 border-t-4 border-b-4 border-green-500' />
+          </div>
+          <p className='text-gray-700 dark:text-gray-300 font-medium text-lg text-center'>
+            正在验证您的身份，请稍候...
+          </p>
+        </div>
+      </div>
+    );
+  } else {
+    return <>{children}</>;
+  }
 }