feat(posts): 类型帖截止时间、抽奖奖品表与悬赏发帖体验

统一投票/悬赏/抽奖截止与状态展示，抽奖支持多奖品行；发帖页悬赏积分对齐表格输入，并在余额不足时于底部就地提示。

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

backend/service/post.go

@@ -22,6 +22,7 @@ var (
 type PostService struct {
 	db      *gorm.DB
 	setting *SettingService
+	devMode bool
 }
 
 func NewPostService(db *gorm.DB) *PostService {
@@ -34,6 +35,12 @@ func (s *PostService) WithSetting(setting *SettingService) *PostService {
 	return s
 }
 
+// WithDevMode 开发态：抽奖同 IP 去重对回环地址放宽
+func (s *PostService) WithDevMode(dev bool) *PostService {
+	s.devMode = dev
+	return s
+}
+
 // PostListQuery 帖子列表查询参数
 type PostListQuery struct {
 	BoardID     uint
@@ -445,6 +452,7 @@ func (s *PostService) GetByIDForViewer(id, viewerID uint, loadActor func() *Acto
 	// 惰性结算：悬赏过期退回 / 抽奖到期开奖
 	_ = s.settleExpiredBountyIfNeeded(&post)
 	_ = s.settleDueLotteryIfNeeded(&post)
+	_ = s.settleDuePollIfNeeded(&post)
 	if post.TypeMeta != "" {
 		var fresh model.Post
 		if err := s.db.Select("type_meta").First(&fresh, post.ID).Error; err == nil {
@@ -729,9 +737,8 @@ func (s *PostService) Create(in CreatePostInput) (*PostDetail, error) {
 		bm.Expired = false
 		bm.AcceptedCommentID = 0
 		if status == model.ContentStatusPublished {
-			days := normalizeExpireDays(bm.ExpireDays, 7, []int{3, 7, 14, 30})
+			bm.EndsAt = resolveEndsAtOnPublish(bm.EndsAt, bm.ExpireDays, 7, []int{3, 7, 14, 30}, now)
 			bm.ExpireDays = 0
-			bm.EndsAt = endsAtFromDays(days, now)
 		}
 		typeMeta, _ = encodeMeta(bm)
 	}
@@ -741,14 +748,26 @@ func (s *PostService) Create(in CreatePostInput) (*PostDetail, error) {
 		if lm.WinnerIDs == nil {
 			lm.WinnerIDs = []uint{}
 		}
+		if lm.Prizes == nil {
+			lm.Prizes = []LotteryPrize{}
+		}
+		lm.Slots = lotterySlotsFromPrizes(lm.Prizes)
 		if status == model.ContentStatusPublished {
-			days := normalizeExpireDays(lm.ExpireDays, 7, []int{1, 3, 7, 14})
+			lm.EndsAt = resolveEndsAtOnPublish(lm.EndsAt, lm.ExpireDays, 7, []int{1, 3, 7, 14}, now)
 			lm.ExpireDays = 0
-			lm.EndsAt = endsAtFromDays(days, now)
 		}
 		typeMeta, _ = encodeMeta(lm)
 	}
 
+	if postType == model.PostTypePoll {
+		pm, _ := parsePollMeta(typeMeta)
+		if status == model.ContentStatusPublished {
+			pm.EndsAt = resolveEndsAtOnPublish(pm.EndsAt, pm.ExpireDays, 7, []int{1, 3, 7, 14}, now)
+			pm.ExpireDays = 0
+		}
+		typeMeta, _ = encodeMeta(pm)
+	}
+
 	post := &model.Post{
 		BoardID: in.BoardID, UserID: in.UserID,
 		Title: title, Content: content, Tags: in.Tags,
@@ -892,9 +911,15 @@ func (s *PostService) Update(actor *Actor, postID, userID uint, in UpdatePostInp
 					neu.Multi = old.Multi
 					neu.Anonymous = old.Anonymous
 					neu.Closed = old.Closed
+					neu.EndsAt = old.EndsAt
+					neu.ClosedAt = old.ClosedAt
+					neu.ExpireDays = 0
 					meta, _ = encodeMeta(neu)
 				} else {
 					neu.Closed = old.Closed
+					neu.EndsAt = old.EndsAt
+					neu.ClosedAt = old.ClosedAt
+					neu.ExpireDays = 0
 					meta, _ = encodeMeta(neu)
 				}
 			}
@@ -907,8 +932,16 @@ func (s *PostService) Update(actor *Actor, postID, userID uint, in UpdatePostInp
 				neu.WinnerIDs = old.WinnerIDs
 				neu.Closed = old.Closed
 				neu.EndsAt = old.EndsAt
-				if old.Drawn {
+				// 已有评论或已开奖：冻结奖品（名额由奖品合计推导）
+				locked := old.Drawn || post.CommentCount > 0
+				if locked {
+					if !lotteryPrizesEqual(neu.Prizes, old.Prizes) || neu.Slots != old.Slots {
+						return nil, ErrLotteryPrizesLocked
+					}
+					neu.Prizes = old.Prizes
 					neu.Slots = old.Slots
+				} else {
+					neu.Slots = lotterySlotsFromPrizes(neu.Prizes)
 				}
 				meta, _ = encodeMeta(neu)
 			}
@@ -920,6 +953,7 @@ func (s *PostService) Update(actor *Actor, postID, userID uint, in UpdatePostInp
 				// 解题态走专用 API，编辑帖子不覆盖
 				neu.Solved = old.Solved
 				neu.AcceptedCommentID = old.AcceptedCommentID
+				neu.SolvedAt = old.SolvedAt
 				meta, _ = encodeMeta(neu)
 			}
 		}