feat(ECR-014): MembershipPlan 套餐配置并 Closed

membership_plans 表、admin 套餐页、Grant/CreateOrder 读表；
Loop continuous 自动 Approve/Closed。Next：ECR-015 RedemptionCode。

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

apps/api/internal/service/membership/service.go

@@ -34,7 +34,17 @@ func (s *Service) CreateOrder(ctx context.Context, userID uuid.UUID, in CreateOr
 	amount := 990
 	plan := in.Plan
 	if in.Kind == "membership" {
-		amount = 2500
+		if plan == "" {
+			plan = "month"
+		}
+		a, err := s.Reports.MembershipPlanAmountCents(ctx, plan)
+		if err != nil {
+			return uuid.Nil, err
+		}
+		if a <= 0 {
+			return uuid.Nil, errors.New("invalid membership plan")
+		}
+		amount = a
 	}
 	if in.Kind == "ask_pack" {
 		if plan == "" {