fix(worker): 防止事务泄漏并恢复滞留队列

为 PostgreSQL 连接增加可配置的事务空闲与锁等待超时，并在请求取消或 Worker 退出后使用独立有界上下文回滚事务。\n\n恢复过期任务时按批次使用 SKIP LOCKED，周期重建缺失或终态 River Job；锁等待超时只在确认尚未提交上游时安全重排，避免重复执行和重复结算。\n\n验证：完整 Go 测试、go vet、生产 Kustomize 渲染、gofmt 与 git diff --check 均通过。

apps/api/internal/store/wallet.go

@@ -163,7 +163,7 @@ func (s *Store) ReserveTaskBilling(ctx context.Context, task GatewayTask, user *
 	reservations := make([]WalletBillingReservation, 0, len(amounts))
 	pricingSnapshotJSON, _ := json.Marshal(sanitizeJSONForStorage(pricingSnapshot))
 	requestFingerprint := walletString(pricingSnapshot["requestFingerprint"])
-	err := pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+	err := s.beginTransaction(ctx, func(tx pgx.Tx) error {
 		for currency, rawAmount := range amounts {
 			amount := roundMoney(rawAmount)
 			if amount <= 0 {
@@ -309,7 +309,7 @@ func (s *Store) reserveTaskBillingExact(ctx context.Context, task GatewayTask, g
 	pricingSnapshotJSON, _ := json.Marshal(sanitizeJSONForStorage(pricingSnapshot))
 	requestFingerprint := walletString(pricingSnapshot["requestFingerprint"])
 	var reservations []WalletBillingReservation
-	err := pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+	err := s.beginTransaction(ctx, func(tx pgx.Tx) error {
 		var positive bool
 		if err := tx.QueryRow(ctx, `SELECT $1::numeric(38, 9) > 0`, amount).Scan(&positive); err != nil {
 			return fmt.Errorf("invalid exact reservation amount: %w", err)
@@ -408,7 +408,7 @@ func (s *Store) ReleaseTaskBillingReservations(ctx context.Context, reservations
 	if reason == "" {
 		reason = "task_not_settled"
 	}
-	return pgx.BeginFunc(ctx, s.pool, func(tx pgx.Tx) error {
+	return s.beginTransaction(ctx, func(tx pgx.Tx) error {
 		taskIDs := map[string]struct{}{}
 		for _, reservation := range reservations {
 			if strings.TrimSpace(reservation.AccountID) == "" {