feat(listings): add source field to PriceHistory + unit tests

- Add `source` column to PriceHistory Prisma model (manual_update, admin_override, market_adjustment)
- Add migration for the new column with default 'manual_update'
- Update ListingPriceChangedEvent domain event with optional source parameter
- Update RecordPriceHistoryHandler to persist source
- Update GetPriceHistoryHandler to return source in query results
- Add unit tests for RecordPriceHistoryHandler (5 cases)
- Add unit tests for GetPriceHistoryHandler (3 cases)
- Add ListingPriceChangedEvent tests to domain events spec (4 cases)
- Add getPriceHistory controller tests (2 cases)

All 1805 tests pass, typecheck clean.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/modules/listings/domain/__tests__/listing-events.spec.ts

@@ -1,6 +1,7 @@
 import { describe, it, expect } from 'vitest';
 import { ListingApprovedEvent } from '../events/listing-approved.event';
 import { ListingCreatedEvent } from '../events/listing-created.event';
+import { ListingPriceChangedEvent } from '../events/listing-price-changed.event';
 import { ListingSoldEvent } from '../events/listing-sold.event';
 import { ListingStatusChangedEvent } from '../events/listing-status-changed.event';
 
@@ -51,6 +52,34 @@ describe('Listings Domain Events', () => {
     });
   });
 
+  describe('ListingPriceChangedEvent', () => {
+    it('creates event with correct properties', () => {
+      const event = new ListingPriceChangedEvent('listing-1', 5_000_000_000n, 6_000_000_000n, 'manual_update');
+
+      expect(event.eventName).toBe('listing.price_changed');
+      expect(event.aggregateId).toBe('listing-1');
+      expect(event.oldPrice).toBe(5_000_000_000n);
+      expect(event.newPrice).toBe(6_000_000_000n);
+      expect(event.source).toBe('manual_update');
+      expect(event.occurredAt).toBeInstanceOf(Date);
+    });
+
+    it('defaults source to manual_update', () => {
+      const event = new ListingPriceChangedEvent('listing-2', 1_000_000n, 2_000_000n);
+      expect(event.source).toBe('manual_update');
+    });
+
+    it('accepts admin_override source', () => {
+      const event = new ListingPriceChangedEvent('listing-3', 1n, 2n, 'admin_override');
+      expect(event.source).toBe('admin_override');
+    });
+
+    it('accepts market_adjustment source', () => {
+      const event = new ListingPriceChangedEvent('listing-4', 1n, 2n, 'market_adjustment');
+      expect(event.source).toBe('market_adjustment');
+    });
+  });
+
   describe('ListingStatusChangedEvent', () => {
     it('creates event with correct properties', () => {
       const event = new ListingStatusChangedEvent('listing-1', 'prop-1', 'DRAFT', 'PENDING_REVIEW');

apps/api/src/modules/listings/domain/events/listing-price-changed.event.ts

@@ -1,5 +1,7 @@
 import type { DomainEvent } from '@modules/shared';
 
+export type PriceChangeSource = 'manual_update' | 'admin_override' | 'market_adjustment';
+
 export class ListingPriceChangedEvent implements DomainEvent {
   readonly eventName = 'listing.price_changed';
   readonly occurredAt = new Date();
@@ -8,5 +10,6 @@ export class ListingPriceChangedEvent implements DomainEvent {
     public readonly aggregateId: string,
     public readonly oldPrice: bigint,
     public readonly newPrice: bigint,
+    public readonly source: PriceChangeSource = 'manual_update',
   ) {}
 }