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/components/Header.tsx

@@ -199,7 +199,7 @@ export default function Header({
       className="sticky top-0 z-50 border-b"
       style={{
         borderColor: "var(--line)",
-        background: "color-mix(in srgb, var(--bg) 82%, transparent)",
+        background: "color-mix(in srgb, var(--panel) 86%, transparent)",
         backdropFilter: "blur(14px)",
         WebkitBackdropFilter: "blur(14px)",
       }}
@@ -426,7 +426,7 @@ function NavPill({
       className="inline-flex items-center gap-1.5 px-3.5 py-2 rounded-full text-[15px] font-semibold transition-colors"
       style={
         active
-          ? { background: "var(--accent-soft)", color: "var(--accent)" }
+          ? { background: "transparent", color: "var(--accent)" }
           : { color: "var(--ink)" }
       }
     >
@@ -451,7 +451,7 @@ function MobileLink({
       className="px-3 py-3 rounded-2xl text-[16px] font-semibold transition-colors"
       style={{
         color: active ? "var(--accent)" : "var(--ink)",
-        background: active ? "var(--accent-soft)" : "transparent",
+        background: "transparent",
       }}
     >
       {children}
@@ -484,7 +484,7 @@ function UserMenu({ user, onLogout }: { user: User; onLogout: () => void }) {
   }, [open]);
 
   const itemCls =
-    "w-full flex items-center gap-2.5 px-4 py-2.5 text-[13.5px] transition-colors hover:bg-[var(--accent-soft)] focus-visible:bg-[var(--accent-soft)]";
+    "w-full flex items-center gap-2.5 px-4 py-2.5 text-[13.5px] transition-colors hover:bg-[var(--panel-2)] focus-visible:bg-[var(--panel-2)]";
 
   return (
     <div className="relative hidden lg:block" ref={menuRef}>