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/app/layout.tsx

@@ -21,6 +21,7 @@ import { getMeCached, getPublicSettingsCached } from "@/lib/serverData";
 import { TOKEN_COOKIE, authCookieHeader } from "@/lib/cookies";
 import { accentStyleCSS } from "@/lib/theme";
 import { bgConfigFromSettings, bgStyleCSS } from "@/lib/bg";
+import { levelVarsCSS } from "@/lib/levels";
 import { siteDocumentTitle } from "@/lib/brand";
 import { motionConfigFromSettings } from "@/lib/motion";
 import { peekPublicMetaSnapshot, publishPublicMetaSnapshot } from "@/lib/publicMetaSnapshot";
@@ -126,6 +127,7 @@ export default async function RootLayout({
     <html
       lang="zh-CN"
       data-j13-chrome={isAdmin ? "admin" : "site"}
+      data-lv-fx={settings.levels_fx === false ? "off" : "on"}
       className={`${theme === "dark" ? "dark" : ""} ${motionHtmlClass} ${jakarta.variable} ${notoSC.variable} ${jetbrainsMono.variable}`.trim()}
     >
       <body className="min-h-screen flex flex-col">
@@ -144,6 +146,12 @@ export default async function RootLayout({
             dangerouslySetInnerHTML={{ __html: bgCSS }}
           />
         ) : null}
+        {/* 等级配色变量（--lv-N-fg/-bg，引用设计 token 随明暗主题切换）；恒渲染兼作兜底 */}
+        <style
+          id="j13-level-vars"
+          data-level-source="ssr"
+          dangerouslySetInnerHTML={{ __html: levelVarsCSS(settings.levels) }}
+        />
         <a href="#main" className="skip-link">
           跳到主要内容
         </a>