[fix] Improve targeted action logging and source validation

[paul-fresquet]

Summary:

• log targeted action validation outcomes with item details
• use ILogger in synchronization rule view model with success/warn/error logs
• split invalid source count into SourceMissing and SourceHasMultipleIdentities with localized messages and tests

Tests:

• dotnet test --filter FullyQualifiedName~SynchronizationRuleGlobalViewModelTests
• dotnet test --filter FullyQualifiedName~TargetedActionGlobalViewModelTests

[sonarqubecloud]

Quality Gate passed

Issues
67 New issues
0 Accepted issues

Measures
0 Security Hotspots
82.1% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud