fix(server): add definite assignment assertions to UpdateUserMembershipDto

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/server/src/user/dto/update-user-membership.dto.ts

@@ -2,7 +2,7 @@ import { IsDateString, IsInt, IsOptional, IsUUID, Min } from 'class-validator'
 
 export class UpdateUserMembershipDto {
   @IsUUID()
-  cardTypeId: string
+  cardTypeId!: string
 
   @IsOptional()
   @IsInt()
@@ -10,8 +10,8 @@ export class UpdateUserMembershipDto {
   remainingTimes?: number | null
 
   @IsDateString()
-  startDate: string
+  startDate!: string
 
   @IsDateString()
-  expireDate: string
+  expireDate!: string
 }