feat: enable TreatWarningsAsErrors

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

Author: HavenDV

src/libs/Directory.Build.props

@@ -50,6 +50,7 @@
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <AnalysisLevel>latest</AnalysisLevel>
     <AnalysisMode>All</AnalysisMode>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
 
   <PropertyGroup Label="Trimmable" Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net6.0'))">