fix(orm): add explicit column types for conversation and order entities

Fixed remaining TypeORM DataTypeNotSupportedError for "Object" type.

## conversation-service/ConversationORM
- title: varchar(255)
- endedAt: timestamptz

## payment-service/OrderORM
- serviceCategory: varchar(100)
- currency: varchar(10)
- paymentMethod: varchar(50)
- paidAt: timestamptz
- completedAt: timestamptz

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/services/conversation-service/src/infrastructure/database/postgres/entities/conversation.orm.ts

@@ -28,7 +28,7 @@ export class ConversationORM {
   @Column({ length: 20, default: 'ACTIVE' })
   status: ConversationStatusType;
 
-  @Column({ nullable: true })
+  @Column({ type: 'varchar', length: 255, nullable: true })
   title: string | null;
 
   @Column({ type: 'text', nullable: true })
@@ -111,7 +111,7 @@ export class ConversationORM {
   @UpdateDateColumn({ name: 'updated_at' })
   updatedAt: Date;
 
-  @Column({ name: 'ended_at', nullable: true })
+  @Column({ name: 'ended_at', type: 'timestamptz', nullable: true })
   endedAt: Date | null;
 
   @OneToMany(() => MessageORM, (message) => message.conversation)

packages/services/payment-service/src/infrastructure/database/postgres/entities/order.orm.ts

@@ -20,28 +20,28 @@ export class OrderORM {
   @Column({ name: 'service_type', type: 'varchar', length: 50 })
   serviceType: string;
 
-  @Column({ name: 'service_category', nullable: true })
+  @Column({ name: 'service_category', type: 'varchar', length: 100, nullable: true })
   serviceCategory: string | null;
 
   @Column({ type: 'decimal', precision: 10, scale: 2 })
   amount: number;
 
-  @Column({ default: 'CNY' })
+  @Column({ type: 'varchar', length: 10, default: 'CNY' })
   currency: string;
 
   @Column({ type: 'varchar', length: 50, default: 'CREATED' })
   status: string;
 
-  @Column({ name: 'payment_method', nullable: true })
+  @Column({ name: 'payment_method', type: 'varchar', length: 50, nullable: true })
   paymentMethod: string | null;
 
   @Column({ name: 'payment_id', type: 'uuid', nullable: true })
   paymentId: string | null;
 
-  @Column({ name: 'paid_at', nullable: true })
+  @Column({ name: 'paid_at', type: 'timestamptz', nullable: true })
   paidAt: Date | null;
 
-  @Column({ name: 'completed_at', nullable: true })
+  @Column({ name: 'completed_at', type: 'timestamptz', nullable: true })
   completedAt: Date | null;
 
   @Column({ type: 'jsonb', nullable: true })