ci(sonar): add sonar-project.properties

Configures SonarCloud analysis for the project:
- Scopes sources and tests to their respective directories
- Excludes build artifacts, generated files, and EF Core migrations
  from analysis and coverage metrics
- Excludes the test project from duplicate code (CPD) detection —
  Fakes, Mocks, and Stubs are intentionally repetitive by design

Co-authored-by: Claude <noreply@anthropic.com>

Author: nanotaboada

sonar-project.properties

@@ -0,0 +1,51 @@
+# =============================================================================
+# SonarCloud configuration
+# https://docs.sonarsource.com/sonarcloud/advanced-setup/analysis-parameters/
+#
+# Project key and organization can be verified in SonarCloud under:
+# Administration → General Settings
+# =============================================================================
+
+sonar.projectKey=nanotaboada_Dotnet.Samples.AspNetCore.WebApi
+sonar.organization=nanotaboada
+
+# Source encoding
+sonar.sourceEncoding=UTF-8
+
+# =============================================================================
+# Sources and tests
+# =============================================================================
+
+sonar.sources=src/
+sonar.tests=test/
+sonar.test.inclusions=test/**/*.cs
+
+# =============================================================================
+# Global exclusions
+# Keeps analysis focused on hand-written production code.
+# =============================================================================
+
+sonar.exclusions=\
+  **/obj/**,\
+  **/bin/**,\
+  **/Migrations/**
+
+# =============================================================================
+# Coverage exclusions
+# Test files and generated/infrastructure code should not count against
+# production code coverage metrics.
+# =============================================================================
+
+sonar.coverage.exclusions=\
+  test/**/*.cs,\
+  **/Migrations/**,\
+  **/Data/PlayerDbContext.cs
+
+# =============================================================================
+# Duplicate code (CPD) exclusions
+# Test utilities (Fakes, Mocks, Stubs) are intentionally repetitive by design:
+# each operation gets its own factory method and the similarity between
+# arrange/act/assert blocks across tests is expected and harmless.
+# =============================================================================
+
+sonar.cpd.exclusions=test/**/*.cs