feat: 外观支持自定义 CSS/JS，并升级发帖工作台与积分存量看板

后台可注入全站 CSS/JS（SSR 生效，CSS 可热换）；发帖/编辑改为锁一屏工作室；经济看板增加存量健康度；主题令牌与弹层误关一并收紧。

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

frontend/app/announcements/page.tsx

@@ -41,7 +41,7 @@ function FeaturedAnnouncement({ a }: { a: Announcement }) {
   return (
     <Link
       href={`/announcement/${a.id}`}
-      className="block px-5 sm:px-6 pt-5 sm:pt-6 pb-5 transition-colors hover:bg-[var(--accent-soft)] focus-visible:bg-[var(--accent-soft)]"
+      className="block px-5 sm:px-6 pt-5 sm:pt-6 pb-5 transition-colors hover:bg-[var(--panel-2)] focus-visible:bg-[var(--panel-2)]"
     >
       <div className="flex items-center gap-2 flex-wrap mb-3">
         <span
@@ -76,7 +76,7 @@ function AnnouncementRow({ a, showDivider }: { a: Announcement; showDivider: boo
   return (
     <Link
       href={`/announcement/${a.id}`}
-      className="block px-5 sm:px-6 py-4 sm:py-5 transition-colors hover:bg-[var(--accent-soft)] focus-visible:bg-[var(--accent-soft)]"
+      className="block px-5 sm:px-6 py-4 sm:py-5 transition-colors hover:bg-[var(--panel-2)] focus-visible:bg-[var(--panel-2)]"
       style={showDivider ? { borderTop: "1px solid var(--line)" } : undefined}
     >
       <div className="flex items-center gap-2 flex-wrap">