feat(phase-7-frontend): anomaly feed UI + nav badge + Settings toggle (+31 bUnit tests)

Frontend portion of Phase 7. Backend (commit a6ff368) had already shipped
the AnomalyDetector, DetectAnomaliesUseCase, AnomalyDetectionPoller, and
all DI wiring. This commit adds the user-facing surfaces.

New surfaces (Option A routing — folder-per-feature):
- Pages/Anomalies/AnomalyFeed.razor (@page /anomalies) — replaces the
  Phase 5 placeholder with a severity-coded card stream, filter chips
  (severity / sport / date), unread-count summary, 'Mark all read' action.
- Pages/Anomalies/Detail.razor (@page /anomalies/{id:guid}) — m-detail-header
  lockup + AnomalyEvidence panel + back link to /events/{eventCode}.

New components:
- AnomalyCard.razor — severity-tinted left border (signal-red on High,
  amber on Medium, neutral on Low) + SeverityBadge pill + sport icon +
  pre→post tabular-mono rate strip + relative time. Click navigates.
- SeverityBadge.razor — small pill mapping score → bucket per backend
  handoff (Low <0.45, Medium <0.60, High ≥0.60).
- AnomalyEvidence.razor — two-column pre/post panel with implied-prob
  bars + raw rates; favourite-swap callout when argmax(p_pre) ≠ argmax(p_post);
  signal-red 3px left border on the post column. Handles 2-way (no draw).

State + service split mirrors Phase 6's pattern:
- AnomalyViewModels.cs — AnomalyListItem / AnomalyDetailVm / Severity enum
  / AnomalyEvidenceSnapshot record. Severity computed in the view-model
  from Score.
- IAnomalyBrowsingService / AnomalyBrowsingService — wraps IAnomalyRepository,
  parses Anomaly.EvidenceJson into typed view-models, applies filters
  client-side. Methods: ListAsync(filter, ct), GetByIdAsync(id, ct),
  GetUnreadCountAsync(since, ct).
- AnomalyBrowsingState — Singleton holding AnomalyFilter (severity threshold,
  sport set, date range) + LastSeenUtc + cached UnreadCount. OnChange event.

Nav badge:
- NavBody.razor subscribes to AnomalyBrowsingState.OnChange, renders a
  pulsing red m-nav__badge when UnreadCount > 0. Badge resets when the
  user clicks 'Mark all read' on the feed toolbar.

Settings toggle:
- Settings.razor — added Workers:AnomalyDetectionEnabled toggle (backend
  added the flag). Localized via Settings.Worker.AnomalyDetectionEnabled.
- Marathon.UI.Services.WorkerOptions mirror — added AnomalyDetectionEnabled
  (default true).

Localization: +30 RU/EN keys following the dot-segmented convention
(Anomaly.*, Settings.Worker.AnomalyDetectionEnabled). Full key parity verified.

Tests (+31 bUnit, all passing):
- AnomalyFeedTests, AnomalyDetailTests
- AnomalyCardTests, SeverityBadgeTests, AnomalyEvidenceTests
- FakeAnomalyBrowsingService support fake registered in MarathonTestContext.

Routing: deleted the Phase 5 Pages/Anomalies.razor placeholder; new feed
page lives at Pages/Anomalies/AnomalyFeed.razor.

Build: 0 warnings, 0 errors.
Tests: Domain 109 + Application 19 + Infrastructure 80 + UI 68 = 276/276
(baseline 245, +31 new bUnit tests, no regressions).

Phase 7 status: ✅ Done (backend + frontend both complete, awaiting review).

Known deferral: AnomalyBrowsingState.LastSeenUtc is in-memory only; the
unread-count badge resets on app restart. Acceptable for now; Phase 9 may
extend ISettingsWriter or add an ILastSeenStore.

src/Marathon.UI/Services/AnomalyViewModels.cs

@@ -0,0 +1,105 @@
+using Marathon.Domain.Enums;
+using Marathon.Domain.ValueObjects;
+
+namespace Marathon.UI.Services;
+
+/// <summary>
+/// Severity bucket derived from <see cref="AnomalyListItem.Score"/>.
+/// Phase 7 mapping (see backend handoff):
+/// Low = [0.30, 0.45), Medium = [0.45, 0.60), High = [0.60, 1.00].
+/// </summary>
+public enum AnomalySeverity
+{
+    Low,
+    Medium,
+    High,
+}
+
+/// <summary>
+/// Filter state passed from a page to <see cref="IAnomalyBrowsingService"/>.
+/// All fields optional — empty filter returns the full feed.
+/// </summary>
+public sealed record AnomalyFilter(
+    AnomalySeverity? MinSeverity = null,
+    IReadOnlyCollection<int>? SportCodes = null,
+    DateTimeOffset? From = null,
+    DateTimeOffset? To = null);
+
+/// <summary>
+/// Compact anomaly row used by the feed page. Designed to render without any
+/// further repository calls — pre-shaped strings + parsed evidence summary.
+/// </summary>
+public sealed record AnomalyListItem(
+    Guid Id,
+    EventId EventId,
+    string EventTitle,
+    SportCode Sport,
+    string CountryCode,
+    string LeagueId,
+    DateTimeOffset DetectedAt,
+    decimal Score,
+    AnomalySeverity Severity,
+    AnomalyKind Kind,
+    int SuspensionGapSeconds,
+    decimal? PreWin1Rate,
+    decimal? PreDrawRate,
+    decimal? PreWin2Rate,
+    decimal? PostWin1Rate,
+    decimal? PostDrawRate,
+    decimal? PostWin2Rate,
+    AnomalyFavourite PreFavourite,
+    AnomalyFavourite PostFavourite,
+    bool IsTwoWay);
+
+/// <summary>
+/// Full anomaly aggregate for the detail page. Carries the parsed evidence
+/// snapshots plus the originating event metadata for the link-back affordance.
+/// </summary>
+public sealed record AnomalyDetailVm(
+    AnomalyListItem Item,
+    AnomalyEvidenceSnapshot Pre,
+    AnomalyEvidenceSnapshot Post);
+
+/// <summary>
+/// Snapshot bracket of the suspension window — pre or post — with raw rates,
+/// implied probabilities, and the side that was the favourite at that moment.
+/// </summary>
+public sealed record AnomalyEvidenceSnapshot(
+    DateTimeOffset CapturedAt,
+    decimal? Rate1,
+    decimal? RateDraw,
+    decimal? Rate2,
+    decimal? P1,
+    decimal? PDraw,
+    decimal? P2,
+    AnomalyFavourite Favourite);
+
+/// <summary>Side that holds the lowest implied probability in a snapshot.</summary>
+public enum AnomalyFavourite
+{
+    Side1,
+    Draw,
+    Side2,
+    None,
+}
+
+/// <summary>Helpers for severity bucketing.</summary>
+public static class AnomalySeverityRules
+{
+    public const decimal LowThreshold = 0.30m;
+    public const decimal MediumThreshold = 0.45m;
+    public const decimal HighThreshold = 0.60m;
+
+    public static AnomalySeverity FromScore(decimal score) => score switch
+    {
+        < MediumThreshold => AnomalySeverity.Low,
+        < HighThreshold => AnomalySeverity.Medium,
+        _ => AnomalySeverity.High,
+    };
+
+    public static bool MeetsThreshold(AnomalySeverity actual, AnomalySeverity? minimum)
+    {
+        if (minimum is null) return true;
+        return (int)actual >= (int)minimum.Value;
+    }
+}