feat: 用户徽章与等级体系，积分经济管理重构

- 新增徽章系统：badge 服务与 handler、管理端配置页、BadgeChip/LevelBadge 展示组件
- 新增等级模型：model/level 及前端 levels 元数据
- 管理端经济模块拆分为 points/badges/levels 独立页面，EconomySettings 迁入设置
- 积分、签到、评论等服务适配等级与徽章逻辑

frontend/components/Header.tsx

@@ -29,6 +29,8 @@ import { onDocumentVisible } from "@/lib/visibilityReconcile";
 import NotificationBell from "./NotificationBell";
 import ThemeToggle from "./ThemeToggle";
 import Avatar from "./Avatar";
+import LevelBadge from "./LevelBadge";
+import BadgeChip from "./BadgeChip";
 import BrandLockup from "./BrandLockup";
 import { useAllowMessages } from "./MessagesPolicyProvider";
 import type { BrandLogoFit, BrandLogoSize, BrandMark } from "@/lib/brand";
@@ -536,8 +538,12 @@ function UserMenu({ user, onLogout }: { user: User; onLogout: () => void }) {
           >
             <Avatar name={user.nickname || user.username} src={user.avatar || undefined} size={38} />
             <div className="min-w-0">
-              <p className="text-[14px] truncate" style={{ color: "var(--ink)" }}>
-                {user.nickname}
+              <p className="text-[14px] truncate flex items-center gap-1.5" style={{ color: "var(--ink)" }}>
+                <span className="truncate">{user.nickname}</span>
+                <LevelBadge level={user.level} />
+                {(user.badges ?? []).slice(0, 2).map((ub) => (
+                  <BadgeChip key={ub.id} badge={ub.badge} />
+                ))}
               </p>
               <p className="meta text-xs truncate">@ {user.username}</p>
             </div>