Task/remove deprecated firstBuyDate from portfolio holding response (#6220)

* Remove deprecated firstBuyDate

* Update changelog

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Changed
+
+- Removed the deprecated `firstBuyDate` from the endpoint `GET api/v1/portfolio/holding/:dataSource/:symbol`
+
 ## 2.232.0 - 2026-01-19
 
 ### Added

apps/api/src/app/portfolio/portfolio.service.ts

@@ -914,7 +914,6 @@ export class PortfolioService {
       );
 
     return {
-      firstBuyDate,
       marketPrice,
       marketPriceMax,
       marketPriceMin,

libs/common/src/lib/interfaces/responses/portfolio-holding-response.interface.ts

@@ -16,10 +16,6 @@ export interface PortfolioHoldingResponse {
   dividendYieldPercent: number;
   dividendYieldPercentWithCurrencyEffect: number;
   feeInBaseCurrency: number;
-
-  /** @deprecated use dateOfFirstActivity */
-  firstBuyDate: string;
-
   grossPerformance: number;
   grossPerformancePercent: number;
   grossPerformancePercentWithCurrencyEffect: number;