feat: 新增大量社区功能与基础组件，优化站点整体体验

- 新增事件总线式toast通知系统
- 新增头像、阅读进度、404/500错误页等基础组件
- 重构页脚、布局、分页、点赞按钮等现有组件
- 新增用户个人页、通知中心、帖子编辑/发布/置顶/推荐管理功能
- 优化登录注册页面样式与交互
- 修复路径类型文件引用，更新站点元信息与字体配置

frontend/app/login/page.tsx

@@ -3,6 +3,7 @@
 import { useState } from "react";
 import { useRouter, useSearchParams } from "next/navigation";
 import Link from "next/link";
+import { MessagesSquare } from "lucide-react";
 import { apiLogin } from "@/lib/api";
 
 export default function LoginPage() {
@@ -32,45 +33,57 @@ export default function LoginPage() {
   };
 
   return (
-    <div className="max-w-md mx-auto mt-12">
-      <h1 className="text-2xl font-bold mb-6 text-center">登录</h1>
-      <form onSubmit={handleSubmit} className="space-y-4">
-        {error && (
-          <div className="p-3 rounded-lg bg-red-50 text-red-600 text-sm">{error}</div>
-        )}
+    <div className="max-w-md mx-auto pt-8 sm:pt-14">
+      <div className="mb-7 text-center">
+        <span
+          className="inline-flex w-14 h-14 rounded-2xl items-center justify-center mb-4"
+          style={{ background: "var(--accent-soft)", color: "var(--accent)" }}
+        >
+          <MessagesSquare size={26} />
+        </span>
+        <h1 className="text-[28px] font-extrabold tracking-tight" style={{ color: "var(--ink)" }}>
+          欢迎回来
+        </h1>
+        <p className="text-sm mt-2" style={{ color: "var(--ink-2)" }}>
+          登录后发帖、评论与点赞
+        </p>
+      </div>
+
+      <form onSubmit={handleSubmit} className="panel p-6 sm:p-7 space-y-4">
+        {error && <div className="alert-error">{error}</div>}
         <div>
-          <label className="block text-sm mb-1" style={{ color: "var(--text-secondary)" }}>用户名</label>
+          <label className="field-label">用户名</label>
           <input
             type="text"
             value={username}
             onChange={(e) => setUsername(e.target.value)}
             required
-            className="w-full px-3 py-2 rounded-lg border"
-            style={{ borderColor: "var(--border)", background: "var(--bg)", color: "var(--text)" }}
+            autoFocus
+            className="field"
+            placeholder="testuser"
           />
         </div>
         <div>
-          <label className="block text-sm mb-1" style={{ color: "var(--text-secondary)" }}>密码</label>
+          <label className="field-label">密码</label>
           <input
             type="password"
             value={password}
             onChange={(e) => setPassword(e.target.value)}
             required
-            className="w-full px-3 py-2 rounded-lg border"
-            style={{ borderColor: "var(--border)", background: "var(--bg)", color: "var(--text)" }}
+            className="field"
+            placeholder="••••••"
           />
         </div>
-        <button
-          type="submit"
-          disabled={loading}
-          className="w-full py-2 rounded-lg text-white disabled:opacity-50"
-          style={{ background: "var(--primary)" }}
-        >
+        <button type="submit" disabled={loading} className="btn btn-primary w-full justify-center mt-2">
           {loading ? "登录中..." : "登录"}
         </button>
       </form>
-      <p className="text-center mt-4 text-sm" style={{ color: "var(--text-secondary)" }}>
-        还没有账号？<Link href="/register" className="hover:underline" style={{ color: "var(--primary)" }}>立即注册</Link>
+
+      <p className="meta text-center mt-5">
+        还没有账号？
+        <Link href="/register" className="ml-1 font-semibold" style={{ color: "var(--accent)" }}>
+          立即注册
+        </Link>
       </p>
     </div>
   );