feat(moderation): 帖评删除占位感知与硬删清场

管理删帖须填类型与理由并展示专用页；评论软删占位、版主可硬删不占楼。

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

backend/handler/post.go

@@ -361,7 +361,7 @@ func (h *Handlers) DownloadPostAttachment(c *gin.Context) {
 	_ = filepath.Base(path)
 }
 
-// DeletePost 删除帖子
+// DeletePost 删除帖子（作者自删或 staff 软删；staff 须提交类型与理由）
 func (h *Handlers) DeletePost(c *gin.Context) {
 	claims := middleware.CurrentUser(c)
 	id, err := strconv.ParseUint(c.Param("id"), 10, 64)
@@ -369,10 +369,30 @@ func (h *Handlers) DeletePost(c *gin.Context) {
 		c.JSON(http.StatusBadRequest, gin.H{"error": "无效的帖子 ID"})
 		return
 	}
-	if err := h.Post.Delete(h.loadActor(claims.ID), uint(id), claims.ID); err != nil {
+	var body struct {
+		DeleteType   string `json:"delete_type"`
+		DeleteReason string `json:"delete_reason"`
+	}
+	_ = c.ShouldBindJSON(&body)
+
+	staffDeleted, authorID, err := h.Post.Delete(
+		h.loadActor(claims.ID),
+		uint(id),
+		claims.ID,
+		service.DeletePostOpts{DeleteType: body.DeleteType, DeleteReason: body.DeleteReason},
+	)
+	if err != nil {
 		respondPostModError(c, err)
 		return
 	}
+	if staffDeleted {
+		label := model.PostDeleteTypeLabel(body.DeleteType)
+		preview := label
+		if body.DeleteReason != "" {
+			preview = label + "：" + body.DeleteReason
+		}
+		h.Notification.Create(authorID, claims.ID, model.NotificationTypeDeleted, uint(id), 0, preview)
+	}
 	c.JSON(http.StatusOK, gin.H{"message": "已删除"})
 }