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

lib/oscillators/dem/Dem.cs

@@ -278,7 +278,6 @@ public sealed class Dem : ITValuePublisher
             double prevHigh = double.NaN;
             double prevLow = double.NaN;
             int idx = 0;
-            int count = 0;
 
             for (int i = 0; i < len; i++)
             {
@@ -302,7 +301,6 @@ public sealed class Dem : ITValuePublisher
                 deMinSum += deMin;
 
                 idx = (idx + 1) % period;
-                count++;
                 prevHigh = h;
                 prevLow = l;