feat: 已发布帖子编辑后进修订审核，通过前保持展示旧内容

- Post 模型新增 PendingTitle/PendingBody 字段，分离已发布内容与待审修订
- Update: approved 帖子编辑写入 Pending 字段，不覆盖正文，不改变发布状态
- Approve: 有 PendingBody 时复制到正式字段后清空，无 PendingBody 走首次审核
- Reject: 有 PendingBody 时仅清空待审修订（保持已发布），无 PendingBody 走普通退回
- 新增 ListPendingRevisions 查询，管理后台独立展示"修订待审核"区域
- 详情页展示"修订审核中"标识，编辑页加载待审内容
- 通过修订后直接覆盖，不保留历史版本

internal/service/post_service.go

@@ -217,11 +217,19 @@ func (s *PostService) Update(postID uint, title, body string) error {
 		return common.ErrPostCannotEdit
 	}
 
+	// 已通过帖子：编辑内容保存为待审修订，不影响当前展示
+	if post.Status == model.PostStatusApproved {
+		post.PendingTitle = title
+		post.PendingBody = body
+		post.RejectReason = "" // 清空旧退回理由
+		return s.repo.Update(post)
+	}
+
+	// 草稿/已退回：直接修改原文（现有逻辑）
 	post.Title = title
 	post.Body = body
 	post.Excerpt = generateExcerpt(body)
 
-	// rejected 状态编辑后自动重置为 draft
 	if post.Status == model.PostStatusRejected {
 		post.Status = model.PostStatusDraft
 		post.RejectReason = ""
@@ -248,12 +256,26 @@ func (s *PostService) SubmitForAudit(postID uint) error {
 	return s.repo.Update(post)
 }
 
-// Approve 审核通过：pending → approved
+// Approve 审核通过：pending → approved；或修订审核通过复制 Pending 到正式字段
 func (s *PostService) Approve(postID uint) error {
 	post, err := s.findPost(postID)
 	if err != nil {
 		return err
 	}
+
+	// 修订审核：将待审内容覆盖到正式字段
+	if post.PendingBody != "" {
+		post.Title = post.PendingTitle
+		post.Body = post.PendingBody
+		post.Excerpt = generateExcerpt(post.PendingBody)
+		post.PendingTitle = ""
+		post.PendingBody = ""
+		post.Status = model.PostStatusApproved
+		post.RejectReason = ""
+		return s.repo.Update(post)
+	}
+
+	// 首次审核通过
 	if post.Status != model.PostStatusPending {
 		return common.ErrPostCannotApprove
 	}
@@ -262,8 +284,7 @@ func (s *PostService) Approve(postID uint) error {
 	return s.repo.Update(post)
 }
 
-// Reject 退回：pending/approved → rejected
-// 独立于锁定：可单独退回（允许作者修改后重审），也可锁定+退回（禁止再投稿）
+// Reject 退回：pending/approved → rejected；修订退回则清空 Pending 保持 approved
 func (s *PostService) Reject(postID uint, reason string) error {
 	post, err := s.findPost(postID)
 	if err != nil {
@@ -272,6 +293,16 @@ func (s *PostService) Reject(postID uint, reason string) error {
 	if post.Status != model.PostStatusPending && post.Status != model.PostStatusApproved {
 		return common.ErrPostCannotReject
 	}
+
+	// 修订退回：清空待审修订，保持已发布内容不变
+	if post.PendingBody != "" {
+		post.PendingTitle = ""
+		post.PendingBody = ""
+		post.RejectReason = reason
+		return s.repo.Update(post)
+	}
+
+	// 普通退回（首次审核）
 	post.Status = model.PostStatusRejected
 	post.RejectReason = reason
 	return s.repo.Update(post)
@@ -316,6 +347,13 @@ func (s *PostService) Restore(postID uint) error {
 	return nil
 }
 
+// ListPendingRevisions 查询有待审修订的帖子（approved 且 PendingBody 不为空）
+func (s *PostService) ListPendingRevisions(keyword string, page, pageSize int) ([]model.Post, int64, error) {
+	return s.listPageable(page, pageSize, func(offset, limit int) ([]model.Post, int64, error) {
+		return s.repo.FindPendingRevisions(keyword, offset, limit)
+	})
+}
+
 // IsPostAccessible 检查用户是否有权限访问/操作帖子（作者或 moderator+）
 func (s *PostService) IsPostAccessible(userID uint, role string, postUserID uint) bool {
 	return userID == postUserID || model.HasMinRole(role, model.RoleModerator)

internal/service/repository.go

@@ -31,7 +31,7 @@ type userAdminStore interface {
 	IncrementTokenVersion(userID uint) error
 }
 
-// postStore PostService 所需的最小仓储接口（ISP：9 个方法）
+// postStore PostService 所需的最小仓储接口（ISP：10 个方法）
 type postStore interface {
 	Create(post *model.Post) error
 	FindByID(id uint) (*model.Post, error)
@@ -39,6 +39,7 @@ type postStore interface {
 	FindPageable(keyword string, offset, limit int) ([]model.Post, int64, error)
 	FindAdminPageable(keyword, status string, offset, limit int) ([]model.Post, int64, error)
 	FindByUserIDAndStatus(userID uint, status string, offset, limit int) ([]model.Post, int64, error)
+	FindPendingRevisions(keyword string, offset, limit int) ([]model.Post, int64, error)
 	Update(post *model.Post) error
 	SoftDelete(id uint) error
 	Restore(id uint) error