refactor: hoist Moscow offset + sport labels into shared helpers (HIGH)

* New Marathon.Domain.ValueObjects.MoscowTime with Offset, Now, and
  EndOfMoscowDay(DateOnly) — replaces ~15 inline TimeSpan.FromHours(3)
  literals across Domain/Application/Infrastructure/UI.
* New Marathon.UI.Services.SportLabels.Resolve(IStringLocalizer, int) —
  replaces 6 near-identical SportLabel switch bodies in EventListShell,
  Events/Detail, Anomalies/AnomalyFeed, Results/ResultsList,
  Results/ResultsLoader, and AnomalyCard. Single source of truth for the
  6/11/22723/43658 sport-code mapping. Pages keep a one-liner wrapper so
  the call sites stay terse.

src/Marathon.Application/UseCases/DetectAnomaliesUseCase.cs

@@ -2,6 +2,7 @@ using Marathon.Application.Abstractions;
 using Marathon.Application.Configuration;
 using Marathon.Domain.AnomalyDetection;
 using Marathon.Domain.Entities;
+using Marathon.Domain.ValueObjects;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 
@@ -24,7 +25,6 @@ namespace Marathon.Application.UseCases;
 /// </remarks>
 public sealed class DetectAnomaliesUseCase
 {
-    private static readonly TimeSpan MoscowOffset     = TimeSpan.FromHours(3);
     private static readonly TimeSpan SnapshotLookback = TimeSpan.FromHours(24);
 
     // Dedup window: two anomalies for the same event within this window are considered duplicates.
@@ -67,7 +67,7 @@ public sealed class DetectAnomaliesUseCase
         var events = await _eventRepo.ListAsync(ct);
         int newAnomalyCount = 0;
 
-        var now  = DateTimeOffset.UtcNow.ToOffset(MoscowOffset);
+        var now  = MoscowTime.Now;
         var from = now - SnapshotLookback;
 
         // Hoisted outside the per-event loop: load existing anomalies ONCE per cycle