Add Stochastic Oscillator implementation and validation tests

- Implemented Stochastic Oscillator (%K and %D) in Stoch.cs with streaming and batch processing capabilities.
- Added validation tests for the Stochastic Oscillator in Stoch.Validation.Tests.cs, ensuring consistency with Skender.Stock.Indicators.
- Created documentation for the Stochastic Oscillator in Stoch.md, detailing its mathematical formula, architecture, parameters, and common pitfalls.
- Updated project file to include necessary numeric libraries for highest and lowest calculations.

lib/oscillators/dpo/Dpo.Quantower.Tests.cs

@@ -0,0 +1,111 @@
+using TradingPlatform.BusinessLayer;
+using QuanTAlib;
+
+namespace QuanTAlib.Tests;
+
+public sealed class DpoIndicatorTests
+{
+    [Fact]
+    public void DpoIndicator_Constructor_SetsDefaults()
+    {
+        var indicator = new DpoIndicator();
+
+        Assert.Equal(20, indicator.Period);
+        Assert.Equal(SourceType.Close, indicator.Source);
+        Assert.True(indicator.ShowColdValues);
+        Assert.Equal("DPO - Detrended Price Oscillator", indicator.Name);
+        Assert.True(indicator.SeparateWindow);
+        Assert.True(indicator.OnBackGround);
+    }
+
+    [Fact]
+    public void DpoIndicator_MinHistoryDepths_EqualsZero()
+    {
+        var indicator = new DpoIndicator { Period = 20 };
+
+        Assert.Equal(0, DpoIndicator.MinHistoryDepths);
+        IWatchlistIndicator watchlistIndicator = indicator;
+        Assert.Equal(0, watchlistIndicator.MinHistoryDepths);
+    }
+
+    [Fact]
+    public void DpoIndicator_ShortName_IncludesParameters()
+    {
+        var indicator = new DpoIndicator { Period = 10 };
+        indicator.Initialize();
+
+        Assert.Contains("DPO", indicator.ShortName, StringComparison.Ordinal);
+        Assert.Contains("10", indicator.ShortName, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void DpoIndicator_SourceCodeLink_IsValid()
+    {
+        var indicator = new DpoIndicator();
+
+        Assert.Contains("github.com", indicator.SourceCodeLink, StringComparison.Ordinal);
+        Assert.Contains("Dpo.Quantower.cs", indicator.SourceCodeLink, StringComparison.Ordinal);
+    }
+
+    [Fact]
+    public void DpoIndicator_Initialize_CreatesInternalDpo()
+    {
+        var indicator = new DpoIndicator { Period = 10 };
+
+        indicator.Initialize();
+
+        Assert.Single(indicator.LinesSeries);
+    }
+
+    [Fact]
+    public void DpoIndicator_ProcessUpdate_HistoricalBar_ComputesValue()
+    {
+        var indicator = new DpoIndicator { Period = 5 };
+        indicator.Initialize();
+
+        var now = DateTime.UtcNow;
+        for (int i = 0; i < 20; i++)
+        {
+            indicator.HistoricalData.AddBar(now.AddMinutes(i), 100 + i, 110 + i, 90 + i, 105 + i);
+
+            var args = new UpdateArgs(UpdateReason.HistoricalBar);
+            indicator.ProcessUpdate(args);
+        }
+
+        double value = indicator.LinesSeries[0].GetValue(0);
+        Assert.True(double.IsFinite(value));
+    }
+
+    [Fact]
+    public void DpoIndicator_ProcessUpdate_NewBar_ComputesValue()
+    {
+        var indicator = new DpoIndicator { Period = 5 };
+        indicator.Initialize();
+
+        var now = DateTime.UtcNow;
+        for (int i = 0; i < 20; i++)
+        {
+            indicator.HistoricalData.AddBar(now.AddMinutes(i), 100 + i, 110 + i, 90 + i, 105 + i);
+        }
+
+        indicator.ProcessUpdate(new UpdateArgs(UpdateReason.HistoricalBar));
+
+        indicator.HistoricalData.AddBar(now.AddMinutes(20), 120, 130, 110, 125);
+        indicator.ProcessUpdate(new UpdateArgs(UpdateReason.NewBar));
+
+        Assert.Equal(2, indicator.LinesSeries[0].Count);
+    }
+
+    [Fact]
+    public void DpoIndicator_Parameters_CanBeChanged()
+    {
+        var indicator = new DpoIndicator { Period = 20 };
+
+        indicator.Period = 10;
+        indicator.Source = SourceType.Open;
+
+        Assert.Equal(10, indicator.Period);
+        Assert.Equal(SourceType.Open, indicator.Source);
+        Assert.Equal(0, DpoIndicator.MinHistoryDepths);
+    }
+}