✨ feat(contracts): add default value for contract renewal creation time

- set default value of created_time field to CURRENT_TIMESTAMP
- ensure creation time is automatically recorded when a contract renewal record is created

src/server/modules/contracts/hetong-renew.entity.ts

@@ -38,7 +38,11 @@ export class HetongRenew {
   @Column({ name: 'user_id', type: 'varchar', length: 50, nullable: true })
   userId?: string;
 
-  @Column({ name: 'created_time', type: 'datetime' })
+  @Column({ 
+    name: 'created_time', 
+    type: 'datetime', 
+    default: () => 'CURRENT_TIMESTAMP' 
+  })
   createdTime!: Date;
 
   @Column({ name: 'created_at', type: 'timestamp', default: () => 'CURRENT_TIMESTAMP' })