修复(#4): 抽奖发奖修正 — 保底奖不参与随机 + 无订阅时按套餐自动新建订阅

- weighted_picker: Pick 排除 is_fallback 保底奖，避免真实奖被"谢谢参与"挤占
- vpn_duration handler: 无活跃订阅且奖品配置 subscribe_id 时，按该套餐在抽奖
  事务内新建订阅并发放时长；未配置则沿用旧的安全跳过
- 补充单测：picker 排除保底奖、vpn_duration 自动新建订阅、draw 端到端链路

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/logic/lottery/handler/vpn_duration.go

@@ -16,8 +16,11 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/google/uuid"
 	"github.com/perfect-panel/server/internal/model/lottery"
+	subscribemodel "github.com/perfect-panel/server/internal/model/subscribe"
 	usermodel "github.com/perfect-panel/server/internal/model/user"
+	"github.com/perfect-panel/server/pkg/uuidx"
 	"gorm.io/gorm"
 )
 
@@ -88,6 +91,9 @@ func (*VPNDurationHandler) ClaimSchema() json.RawMessage { return nil }
 // vpnDurationConfig 是奖品 Config JSON 的解码目标。
 type vpnDurationConfig struct {
 	DurationDays int `json:"duration_days"`
+	// SubscribeId 指定“无活跃订阅时新建订阅”所用的套餐计划 ID。
+	// 0 表示不新建：延续历史行为（无活跃订阅则记录 skipped 不发放）。
+	SubscribeId int64 `json:"subscribe_id"`
 }
 
 // vpnDurationPayload 落库到 lottery_grant_ledger.payload，用于幂等重放时返回同一
@@ -151,7 +157,25 @@ func (h *VPNDurationHandler) Dispatch(ctx context.Context, tx *gorm.DB, req lott
 	// 未存在 → 真实发放。查用户的活跃订阅。
 	activeSub, findErr := h.findActiveSubscribe(ctx, effectiveUserID)
 	if errors.Is(findErr, gorm.ErrRecordNotFound) {
-		// 与 grantGiftDays 一致：无活跃订阅时记录 skipped 但不失败。
+		// 无活跃订阅：
+		//  - 若奖品配置了 subscribe_id，则按该套餐新建一条订阅并发放时长；
+		//  - 否则延续旧行为：记录 skipped 但不失败（避免抽奖事务因无处发放而回滚）。
+		if cfg.SubscribeId > 0 {
+			newSub, createErr := h.createSubscription(ctx, tx, effectiveUserID, req.DrawId, cfg)
+			if createErr != nil {
+				return lottery.DispatchResult{}, fmt.Errorf("auto-create subscribe for user %d: %w", effectiveUserID, createErr)
+			}
+			payload := vpnDurationPayload{
+				EffectiveUserID: effectiveUserID,
+				SubscribeID:     newSub.Id,
+				Days:            cfg.DurationDays,
+				Message:         fmt.Sprintf("已新建订阅并加 %d 天", cfg.DurationDays),
+			}
+			if err := h.writeBackPayload(ctx, tx, row.Id, payload); err != nil {
+				return lottery.DispatchResult{}, err
+			}
+			return lottery.DispatchResult{State: lottery.DispatchStateAutoClaimed, Message: payload.Message}, nil
+		}
 		payload := vpnDurationPayload{
 			EffectiveUserID: effectiveUserID,
 			Days:            cfg.DurationDays,
@@ -225,6 +249,41 @@ func (h *VPNDurationHandler) findActiveSubscribe(ctx context.Context, userID int
 	return &fallback, nil
 }
 
+// createSubscription 在无活跃订阅时，按奖品配置的 subscribe_id 套餐为用户新建一条
+// 订阅，时长为 cfg.DurationDays 天。套餐属性（流量、节点组）继承自计划，token/uuid
+// 现场生成。整个操作在 caller 的事务内完成，随抽奖事务一起提交/回滚。
+func (h *VPNDurationHandler) createSubscription(ctx context.Context, tx *gorm.DB, userID, drawID int64, cfg vpnDurationConfig) (*usermodel.Subscribe, error) {
+	if tx == nil {
+		return nil, errors.New("createSubscription requires a transaction")
+	}
+	var plan subscribemodel.Subscribe
+	if err := tx.WithContext(ctx).Where("id = ?", cfg.SubscribeId).First(&plan).Error; err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			return nil, fmt.Errorf("subscribe plan %d not found", cfg.SubscribeId)
+		}
+		return nil, err
+	}
+	now := time.Now()
+	// token 需全局唯一：用 lottery draw 维度做种子，避免与订单 token 冲突。
+	tokenSeed := fmt.Sprintf("lottery:%d:%d:%d", cfg.SubscribeId, userID, drawID)
+	newSub := &usermodel.Subscribe{
+		UserId:      userID,
+		OrderId:     0,
+		SubscribeId: plan.Id,
+		NodeGroupId: plan.NodeGroupId,
+		StartTime:   now,
+		ExpireTime:  now.Add(time.Duration(cfg.DurationDays) * 24 * time.Hour),
+		Traffic:     plan.Traffic,
+		Token:       uuidx.SubscribeToken(tokenSeed),
+		UUID:        uuid.New().String(),
+		Status:      1,
+	}
+	if err := tx.WithContext(ctx).Create(newSub).Error; err != nil {
+		return nil, err
+	}
+	return newSub, nil
+}
+
 func (h *VPNDurationHandler) writeBackPayload(ctx context.Context, tx *gorm.DB, ledgerID int64, payload vpnDurationPayload) error {
 	raw, err := json.Marshal(payload)
 	if err != nil {