feat: add 8 new indicators with full integration

New indicators:
- HWC (Holt-Winters Channel) — channels, 27 tests
- VWMACD (Volume-Weighted MACD) — momentum, 38 tests
- Squeeze Pro — oscillators, 69 tests
- BW_MFI (Bill Williams MFI) — oscillators
- DSTOCH (Double Stochastic) — oscillators
- ATRSTOP (ATR Trailing Stop) — reversals
- VSTOP (Volatility Stop) — reversals
- Convexity (Beta Convexity) — statistics, 23 tests

Integration:
- Python bridge: Exports.cs, _bridge.py, wrapper modules
- Documentation: _sidebar.md, _index.md pages, SPEC.md
- All analyzer warnings fixed (MA0074, xUnit2013, S2699)

Build: 0 warnings, 0 errors | Tests: 15,933 passed, 0 failed

lib/reversals/vstop/Vstop.Quantower.cs

@@ -0,0 +1,54 @@
+using System.Drawing;
+using System.Runtime.CompilerServices;
+using TradingPlatform.BusinessLayer;
+
+namespace QuanTAlib;
+
+[SkipLocalsInit]
+public sealed class VstopIndicator : Indicator, IWatchlistIndicator
+{
+    [InputParameter("Period", sortIndex: 0, 2, 500, 1, 0)]
+    public int Period { get; set; } = 7;
+
+    [InputParameter("Multiplier", sortIndex: 1, 0.1, 20.0, 0.1, 1)]
+    public double Multiplier { get; set; } = 3.0;
+
+    [InputParameter("Show cold values", sortIndex: 21)]
+    public bool ShowColdValues { get; set; } = true;
+
+    private Vstop _indicator = null!;
+    private readonly LineSeries _sarSeries;
+
+    public static int MinHistoryDepths => 0;
+    int IWatchlistIndicator.MinHistoryDepths => MinHistoryDepths;
+
+    public override string ShortName => $"VSTOP({Period},{Multiplier:F1})";
+    public override string SourceCodeLink => "https://github.com/mihakralj/QuanTAlib/blob/main/lib/reversals/vstop/Vstop.cs";
+
+    public VstopIndicator()
+    {
+        OnBackGround = true;
+        SeparateWindow = false;
+        Name = "VSTOP - Volatility Stop";
+        Description = "ATR-based trailing stop. Tracks SIC (Significant Close) and flips on reversal.";
+
+        _sarSeries = new LineSeries(name: "VSTOP", color: Color.OrangeRed, width: 2, style: LineStyle.Dot);
+
+        AddLineSeries(_sarSeries);
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected override void OnInit()
+    {
+        _indicator = new Vstop(Period, Multiplier);
+        base.OnInit();
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    protected override void OnUpdate(UpdateArgs args)
+    {
+        _ = _indicator.Update(this.GetInputBar(args), args.IsNewBar());
+
+        _sarSeries.SetValue(_indicator.SarValue, _indicator.IsHot, ShowColdValues);
+    }
+}