feat(hide): 密码可见隐藏块，发帖双栏预览与门禁体验修复

增加密码解锁与游客签名 cookie；发帖页对齐 1440 并默认双栏预览；修复 locked 解析、按钮对比度与回复聚焦。

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

frontend/app/post/[id]/edit/page.tsx

@@ -37,7 +37,7 @@ export default async function EditPostPage({ params }: PageProps) {
   return (
     <div
       data-compose-viewport
-      className="j13-compose-page w-full max-w-6xl mx-auto"
+      className="j13-compose-page w-full"
     >
       <nav className="meta mb-4 flex items-center gap-1.5 flex-wrap text-[13px] shrink-0">
         <Link href="/" className="hover:text-[var(--accent)] transition-colors">

frontend/app/post/[id]/page.tsx

@@ -24,7 +24,7 @@ import {
   type Board,
   type CommentsResponse,
 } from "@/lib/api";
-import { authCookieHeader } from "@/lib/cookies";
+import { postViewerCookieHeader } from "@/lib/cookies";
 import { getMeCached, getPublicSettingsCached } from "@/lib/serverData";
 import CommentSection from "@/components/CommentSection";
 import PostActions from "@/components/PostActions";
@@ -52,7 +52,7 @@ export async function generateMetadata({ params }: PageProps): Promise<Metadata>
   const { id } = await params;
   try {
     // 带登录态：作者/管理团队看待审帖时标签标题也应是真实标题而非"帖子不存在"
-    const { post } = await fetchPostDetail(id, authCookieHeader(await cookies()));
+    const { post } = await fetchPostDetail(id, postViewerCookieHeader(await cookies()));
     if (post.tombstone) {
       return {
         title: post.title || "帖子已删除",
@@ -402,7 +402,7 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
   const { id } = await params;
   const sp = await searchParams;
   const commentPage = Math.max(1, parseInt(sp.page || "1", 10) || 1);
-  const cookie = authCookieHeader(await cookies());
+  const cookie = postViewerCookieHeader(await cookies());
   // 待审/被拒帖子对无权访问者由后端返回 404，这里落到全局 not-found 页而非 500
   let post: Awaited<ReturnType<typeof fetchPostDetail>>["post"];
   try {