fix(conversations): implement soft-delete for conversation deletion

The delete conversation endpoint was a no-op — it verified ownership but
never actually modified the record. Users saw conversations disappear
(frontend optimistic removal) but they reappeared on refresh.

Changes:
- conversation.entity.ts: Add DELETED status, softDelete() and isDeleted()
- conversation.service.ts: Call softDelete() + update instead of no-op
- conversation-postgres.repository.ts: Exclude DELETED conversations
  from findByUserId() queries so they don't appear in user's list

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

packages/services/conversation-service/src/adapters/outbound/persistence/conversation-postgres.repository.ts

@@ -38,7 +38,8 @@ export class ConversationPostgresRepository
     options?: { status?: ConversationStatusType; limit?: number },
   ): Promise<ConversationEntity[]> {
     const queryBuilder = this.createTenantQueryBuilder('conversation')
-      .andWhere('conversation.user_id = :userId', { userId });
+      .andWhere('conversation.user_id = :userId', { userId })
+      .andWhere('conversation.status != :deletedStatus', { deletedStatus: 'DELETED' });
 
     if (options?.status) {
       queryBuilder.andWhere('conversation.status = :status', { status: options.status });

packages/services/conversation-service/src/application/services/conversation.service.ts

@@ -308,11 +308,9 @@ export class ConversationService {
    * Delete a conversation and its messages
    */
   async deleteConversation(conversationId: string, userId: string): Promise<void> {
-    // Verify user owns the conversation
-    await this.getConversation(conversationId, userId);
-
-    // Note: In a real application, you'd want to delete messages in the repository
-    // For now, we rely on database cascade or separate cleanup
+    const conversation = await this.getConversation(conversationId, userId);
+    conversation.softDelete();
+    await this.conversationRepo.update(conversation);
   }
 
   /**

packages/services/conversation-service/src/domain/entities/conversation.entity.ts

@@ -5,6 +5,7 @@ export const ConversationStatus = {
   ACTIVE: 'ACTIVE',
   ENDED: 'ENDED',
   ARCHIVED: 'ARCHIVED',
+  DELETED: 'DELETED',
 } as const;
 
 export type ConversationStatusType =
@@ -236,6 +237,11 @@ export class ConversationEntity {
     this.updatedAt = new Date();
   }
 
+  softDelete(): void {
+    this.status = ConversationStatus.DELETED;
+    this.updatedAt = new Date();
+  }
+
   isActive(): boolean {
     return this.status === ConversationStatus.ACTIVE;
   }
@@ -243,4 +249,8 @@ export class ConversationEntity {
   isEnded(): boolean {
     return this.status === ConversationStatus.ENDED;
   }
+
+  isDeleted(): boolean {
+    return this.status === ConversationStatus.DELETED;
+  }
 }