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.

src/Marathon.UI/Components/AnomalyCard.razor

@@ -211,10 +211,11 @@
 
     private string KindLabel(AnomalyKind kind) => kind switch
     {
-        AnomalyKind.SuspensionFlip   => L["Anomaly.Kind.SuspensionFlip"],
-        AnomalyKind.SteamMove        => L["Anomaly.Kind.SteamMove"],
-        AnomalyKind.SuspensionFreeze => L["Anomaly.Kind.SuspensionFreeze"],
-        _                            => kind.ToString(),
+        AnomalyKind.SuspensionFlip       => L["Anomaly.Kind.SuspensionFlip"],
+        AnomalyKind.SteamMove            => L["Anomaly.Kind.SteamMove"],
+        AnomalyKind.SuspensionFreeze     => L["Anomaly.Kind.SuspensionFreeze"],
+        AnomalyKind.OverroundCompression => L["Anomaly.Kind.OverroundCompression"],
+        _                                => kind.ToString(),
     };
 
     private string SportLabel(int code) => SportLabels.Resolve(L, code);