完善角色与消息权限：收紧板管内容处置，彻底删除仅站长，并统一管理删帖/评弹窗。

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

frontend/components/Header.tsx

@@ -21,7 +21,7 @@ import {
 } from "lucide-react";
 import { apiLogout, apiMe, apiChatUnreadSummary, type User } from "@/lib/api";
 import { hasAuthCookieHint } from "@/lib/cookies";
-import { isStaff } from "@/lib/roles";
+import { canAccessAdminMessages, isStaff } from "@/lib/roles";
 import { onUserUpdate, onForceLogout } from "@/lib/userEvents";
 import { realtime, RT_CHAT_UNREAD } from "@/lib/realtime";
 import type { RtChatUnreadData } from "@/lib/realtime";
@@ -396,7 +396,7 @@ export default function Header({
               </MobileLink>
             )}
             {user && <MobileLink href="/settings">账号设置</MobileLink>}
-            {user && isStaff(user.role) && (
+            {user && (isStaff(user.role) || canAccessAdminMessages(user)) && (
               <MobileLink href="/admin">
                 <span className="inline-flex items-center gap-2"><ShieldCheck size={15} /> 管理面板</span>
               </MobileLink>
@@ -560,7 +560,7 @@ function UserMenu({ user, onLogout }: { user: User; onLogout: () => void }) {
               <Settings size={15} style={{ color: "var(--ink-3)" }} /> 账号设置
             </Link>
           </div>
-          {isStaff(user.role) && (
+          {(isStaff(user.role) || canAccessAdminMessages(user)) && (
             <div className="p-1.5" style={{ borderTop: "1px solid var(--line)" }}>
               <Link href="/admin" onClick={() => setOpen(false)} className={itemCls} role="menuitem">
                 <ShieldCheck size={15} style={{ color: "var(--accent)" }} /> 管理面板