chore: repo cleanup and code quality improvements

- Remove global.json (SDK pinning unnecessary)

- Remove nuget.config, move MyGet source to .csproj RestoreAdditionalProjectSources

- Gitignore ndepend/ entirely, move badges to docs/img/

- Update README.md and docs/ndepend.md badge paths

- Add NDepend project property to QuanTAlib.slnx

- Expand .editorconfig ReSharper/diagnostic suppressions

- Use ArgumentOutOfRangeException instead of ArgumentException

- Use discard _ for unused event sender parameters

- Remove quantalib.code-workspace and sonar-suppressions.json

- Add filter signature SVGs

.gitignore

@@ -36,9 +36,8 @@ bld/
 *.coverage
 *.coveragexml
 
-# NDepend
-ndepend/NDependOut/
-ndepend/coverage/
+# NDepend (entire directory — tooling + generated output)
+ndepend/
 
 # BenchmarkDotNet
 BenchmarkDotNet.Artifacts/
@@ -49,7 +48,7 @@ BenchmarkDotNet.Artifacts/
 
 # Temporary files and agent workspace
 temp/
-temp_pandas_ta/
+pandas_ta/
 temp_decompile/
 Invoke-WebRequest/
 .temp/