feat: 类型帖互动、积分经济与发帖体验

补齐问答采纳/重开、投票匿名与有票禁编、悬赏过期退回、抽奖回帖开奖，并接入积分账本与发帖附件可见性。

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

backend/model/db.go

@@ -39,10 +39,23 @@ func InitDB(dsn string) error {
 		&User{}, &Board{}, &Post{}, &Comment{}, &RefreshToken{}, &Like{}, &Notification{}, &Checkin{},
 		&Announcement{}, &SiteSetting{}, &Attachment{}, &UserBoard{}, &LoginLog{},
 		&ChatRoom{}, &ChatRoomMember{}, &ChatMessage{},
+		&PointLedger{}, &PostContentUnlock{}, &PostAttachment{}, &PostAttachmentUnlock{},
+		&PostPollVote{}, &PostLotteryEntry{},
 	); err != nil {
 		return fmt.Errorf("自动迁移失败: %w", err)
 	}
 
+	// 旧 post_type=normal → discussion
+	if err := db.Exec(`UPDATE posts SET post_type = ? WHERE post_type = ? OR post_type = '' OR post_type IS NULL`,
+		PostTypeDiscussion, PostTypeNormal).Error; err != nil {
+		return fmt.Errorf("帖子类型归一失败: %w", err)
+	}
+
+	// 一次性：用签到累计回填 User.Points（仅余额仍为 0 且有签到积分的用户）
+	if err := backfillPointsFromCheckin(db); err != nil {
+		return fmt.Errorf("积分余额回填失败: %w", err)
+	}
+
 	// RBAC：把初始管理员（id 最小的 admin，通常即首个注册账号）升级为站长；
 	// 已存在 owner 时不动数据，保证幂等
 	if err := ensureOwnerRole(db); err != nil {
@@ -213,6 +226,46 @@ func ensureOwnerRole(db *gorm.DB) error {
 	return nil
 }
 
+// backfillPointsFromCheckin 把历史签到积分写入 User.Points（幂等：仅 points=0 且有签到）
+func backfillPointsFromCheckin(db *gorm.DB) error {
+	type row struct {
+		UserID uint
+		Total  int
+	}
+	var rows []row
+	if err := db.Raw(`
+		SELECT c.user_id, COALESCE(SUM(c.points), 0)::int AS total
+		FROM checkins c
+		INNER JOIN users u ON u.id = c.user_id AND u.deleted_at IS NULL AND u.points = 0
+		GROUP BY c.user_id
+		HAVING COALESCE(SUM(c.points), 0) > 0
+	`).Scan(&rows).Error; err != nil {
+		return err
+	}
+	for _, r := range rows {
+		err := db.Transaction(func(tx *gorm.DB) error {
+			if err := tx.Model(&User{}).Where("id = ? AND points = 0", r.UserID).
+				Update("points", r.Total).Error; err != nil {
+				return err
+			}
+			return tx.Create(&PointLedger{
+				UserID:  r.UserID,
+				Delta:   r.Total,
+				Balance: r.Total,
+				Reason:  PointReasonMigrateCheckin,
+				Note:    "历史签到积分回填",
+			}).Error
+		})
+		if err != nil {
+			return err
+		}
+	}
+	if len(rows) > 0 {
+		log.Printf("[model] 已回填 %d 名用户的签到积分余额", len(rows))
+	}
+	return nil
+}
+
 // seedDefaultBoards 写入默认板块
 func seedDefaultBoards(db *gorm.DB) {
 	defaults := []Board{