feat: 评论/帖子编辑历史与编辑标记，内容锁定

- 新增 smartDiff 差异计算与 EditHistoryModal 编辑历史弹窗，替换原 CommentEditHistoryModal
- 新增 PostEditedMark 编辑标记展示
- 新增内容锁定机制（content_lock）防止并发编辑冲突
- 审核与通知服务适配

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

@@ -37,6 +37,7 @@ import BadgeChip from "@/components/BadgeChip";
 import MarkdownBody from "@/components/MarkdownBody";
 import { publicMarkdownForSeo } from "@/lib/hideBlocks";
 import PostAttachments from "@/components/PostAttachments";
+import PostEditedMark from "@/components/PostEditedMark";
 import PostInteractPanels, { QuestionStatusCard } from "@/components/PostInteractPanels";
 import AcceptedAnswerCard from "@/components/AcceptedAnswerCard";
 import { canModerateBoard } from "@/lib/roles";
@@ -323,8 +324,7 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
   const toc = extractToc(publicBody);
   const headingToc = markdownHeadingToc(toc);
   const readingMinutes = estimateReadingMinutes(publicBody, post.title.length);
-  const edited =
-    new Date(post.updated_at).getTime() - new Date(post.created_at).getTime() > 60_000;
+  const edited = post.edited ?? false;
 
   // 侧栏布局：post 范围左右两列（toc 需在下方已就绪）
   const sidebarLists = sidebarScopeLists(sidebar.config, "post");
@@ -560,6 +560,9 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
                     pinned={post.pinned}
                     recommended={post.recommended}
                     status={post.status}
+                    createdAt={post.created_at}
+                    locked={post.locked}
+                    postEditLockHours={publicSettings.post_edit_lock_hours}
                     title={post.title}
                   />
                 </div>
@@ -586,6 +589,16 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
                       <>
                         {" "}
                         · 更新于 <time dateTime={post.updated_at}>{formatDateTime(post.updated_at)}</time>
+                        {me.user && (
+                          <>
+                            {" "}·{" "}
+                            <PostEditedMark
+                              postId={post.id}
+                              currentTitle={post.title}
+                              currentContent={post.content || ""}
+                            />
+                          </>
+                        )}
                       </>
                     )}
                   </p>
@@ -670,6 +683,9 @@ export default async function PostDetailPage({ params, searchParams }: PageProps
                 page={commentsData.page}
                 size={commentsData.size}
                 user={me.user}
+                postLocked={post.locked}
+                commentEditLockHours={publicSettings.comment_edit_lock_hours}
+                necroReply={post.necro_reply}
                 acceptMode={acceptMode}
                 acceptedCommentId={
                   post.question?.accepted_comment_id ||