✨ feat(user-cards): add unique constraint to cardNo field

- add unique: true to cardNo column to ensure card number uniqueness

src/server/modules/user-cards/user-card.entity.ts

@@ -13,7 +13,7 @@ export class UserCard {
   @Column({ name: 'agent_id', type: 'int', unsigned: true, nullable: true, comment: '代理商ID' })
   agentId!: number | null;
 
-  @Column({ name: 'card_no', type: 'varchar', length: 20, comment: '卡号' })
+  @Column({ name: 'card_no', type: 'varchar', length: 20, unique: true, comment: '卡号' })
   cardNo!: string;
 
   @Column({ name: 'sjt_card_no', type: 'varchar', length: 20, nullable: true, comment: '盛京通卡卡号' })