docs(readme): fix Codecov badge URL to use branch/master

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

Author: nanotaboada

README.md

@@ -4,7 +4,7 @@
 [![.NET CD](https://github.com/nanotaboada/Dotnet.Samples.AspNetCore.WebApi/actions/workflows/dotnet-cd.yml/badge.svg)](https://github.com/nanotaboada/Dotnet.Samples.AspNetCore.WebApi/actions/workflows/dotnet-cd.yml)
 [![CodeQL](https://github.com/nanotaboada/Dotnet.Samples.AspNetCore.WebApi/actions/workflows/github-code-scanning/codeql/badge.svg)](https://github.com/nanotaboada/Dotnet.Samples.AspNetCore.WebApi/actions/workflows/github-code-scanning/codeql)
 [![Quality Gate Status](https://sonarcloud.io/api/project_badges/measure?project=nanotaboada_Dotnet.Samples.AspNetCore.WebApi&metric=alert_status)](https://sonarcloud.io/summary/new_code?id=nanotaboada_Dotnet.Samples.AspNetCore.WebApi)
-[![codecov](https://codecov.io/gh/nanotaboada/Dotnet.Samples.AspNetCore.WebApi/graph/badge.svg?token=hgJc1rStJ9)](https://codecov.io/gh/nanotaboada/Dotnet.Samples.AspNetCore.WebApi)
+[![codecov](https://codecov.io/gh/nanotaboada/Dotnet.Samples.AspNetCore.WebApi/branch/master/graph/badge.svg?token=hgJc1rStJ9)](https://codecov.io/gh/nanotaboada/Dotnet.Samples.AspNetCore.WebApi)
 [![CodeFactor](https://www.codefactor.io/repository/github/nanotaboada/Dotnet.Samples.AspNetCore.WebApi/badge)](https://www.codefactor.io/repository/github/nanotaboada/Dotnet.Samples.AspNetCore.WebApi)
 [![License: MIT](https://img.shields.io/badge/License-MIT-3DA639.svg)](https://opensource.org/licenses/MIT)
 ![Dependabot](https://img.shields.io/badge/Dependabot-contributing-025E8C?logo=dependabot&logoColor=white&labelColor=181818)