feat: 交付官方 Docker 运行时，外观改背景图并下线自定义 CSS/JS

站点/后台分轨背景与用户列表排序一并落地；生产 CORS 改走 SITE_URL，健康检查带版本号。

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/app/layout.tsx

@@ -18,6 +18,7 @@ import type { User } from "@/lib/api";
 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 { motionConfigFromSettings } from "@/lib/motion";
 
 // 构建期下载并自托管字体：同源加载 + 自动 preload + fallback 度量校正，
@@ -83,12 +84,14 @@ export default async function RootLayout({
   const settings = await getPublicSettingsCached();
   const accent = settings.accent;
   const accentCSS = accentStyleCSS(accent || "");
-  const customCSS = (settings.custom_css || "").trim();
-  const customJS = (settings.custom_js || "").trim();
+  const bgCfg = bgConfigFromSettings(settings);
+  const bgCSS = bgStyleCSS(bgCfg);
   const motionCfg = motionConfigFromSettings(settings);
   const motionHtmlClass = [
     !motionCfg.ui_animations ? "j13-reduce-motion" : "",
     motionCfg.ui_animations && !motionCfg.anim_chrome ? "j13-reduce-chrome" : "",
+    bgCfg.bg_site_url ? "j13-has-site-bg" : "",
+    bgCfg.bg_admin_url ? "j13-has-admin-bg" : "",
   ]
     .filter(Boolean)
     .join(" ");
@@ -108,6 +111,7 @@ export default async function RootLayout({
   return (
     <html
       lang="zh-CN"
+      data-j13-chrome={isAdmin ? "admin" : "site"}
       className={`${theme === "dark" ? "dark" : ""} ${motionHtmlClass} ${jakarta.variable} ${notoSC.variable} ${jetbrainsMono.variable}`.trim()}
     >
       <body className="min-h-screen flex flex-col">
@@ -119,11 +123,11 @@ export default async function RootLayout({
             dangerouslySetInnerHTML={{ __html: accentCSS }}
           />
         ) : null}
-        {customCSS ? (
+        {bgCSS ? (
           <style
-            id="j13-custom-css"
-            data-custom-css-source="ssr"
-            dangerouslySetInnerHTML={{ __html: customCSS }}
+            id="j13-bg-vars"
+            data-bg-source="ssr"
+            dangerouslySetInnerHTML={{ __html: bgCSS }}
           />
         ) : null}
         <a href="#main" className="skip-link">
@@ -156,12 +160,9 @@ export default async function RootLayout({
         <Toaster />
         <TipHost />
         <AccountGuard />
-        <ThemeSync initialAccent={accent || ""} initialCustomCSS={customCSS} />
+        <ThemeSync initialAccent={accent || ""} initialBg={bgCfg} />
         <VisitBeacon />
         <RealtimeProvider userId={user ? user.id : null} />
-        {customJS ? (
-          <script id="j13-custom-js" dangerouslySetInnerHTML={{ __html: customJS }} />
-        ) : null}
       </body>
     </html>
   );