feat(anomaly): overround-compression detector

Adds the 4th IAnomalyDetector: flags a sharp drop in the bookmaker's
overround (raw implied-probability sum / margin) over a continuous live
window. Informational/non-directional — excluded from outcome grading
and backtest staking via AnomalyKind.IsDirectional().

- OverroundCompressionDetector: sliding-window scan mirroring SteamMove,
  score = min(1, compression / 0.10 reference), suspension-gap aware.
- MatchWinEvidence.Probabilities gains Overround (pre-normalisation
  margin); evidence JSON shape unchanged.
- Wired into DetectAnomaliesUseCase fan-out; AnomalyOptions + appsettings
  (window 120s, threshold 0.02); en/ru resx + KindLabel arms.
- 11 detector tests incl. score saturation/scaling, inclusive threshold
  boundary, and a three-way (draw-leg) overround case.

tests/Marathon.Domain.Tests/Enums/AnomalyKindExtensionsTests.cs

@@ -9,6 +9,7 @@ public sealed class AnomalyKindExtensionsTests
     [InlineData(AnomalyKind.SuspensionFlip, true)]
     [InlineData(AnomalyKind.SteamMove, true)]
     [InlineData(AnomalyKind.SuspensionFreeze, false)]
+    [InlineData(AnomalyKind.OverroundCompression, false)]
     public void IsDirectional_Should_ClassifyKinds(AnomalyKind kind, bool expected)
     {
         kind.IsDirectional().Should().Be(expected);