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/Pages/Anomalies/Detail.razor

@@ -0,0 +1,113 @@
+@page "/anomalies/{Id:guid}"
+@using Marathon.UI.Components
+@inject IStringLocalizer<SharedResource> L
+@inject IAnomalyBrowsingService Anomalies
+@inject NavigationManager Nav
+
+<PageTitle>@L["App.Title"] · @L["Anomaly.Title"]</PageTitle>
+
+<section class="m-shell">
+    @if (_loading && _detail is null)
+    {
+        <div class="m-list-empty">
+            <MudProgressCircular Indeterminate="true" Size="Size.Small" />
+            <span class="m-mono">@L["Common.Loading"]</span>
+        </div>
+    }
+    else if (_detail is null)
+    {
+        <div class="m-list-empty">
+            <span class="m-kicker" style="border-color: var(--m-c-ink-soft); color: var(--m-c-ink-soft);">404</span>
+            <p style="color: var(--m-c-ink-soft);">@L["Anomaly.Detail.NotFound"]</p>
+            <MudButton Variant="Variant.Outlined" OnClick='() => Nav.NavigateTo("/anomalies")'>
+                @L["Anomaly.Detail.BackToFeed"]
+            </MudButton>
+        </div>
+    }
+    else
+    {
+        <header class="m-detail-header m-rise m-rise-1">
+            <div class="m-detail-header__lockup">
+                <span class="m-kicker" style="color: var(--m-c-anomaly); border-color: var(--m-c-anomaly);">
+                    @KindLabel(_detail.Item.Kind) · @_detail.Item.CountryCode · @_detail.Item.LeagueId
+                </span>
+                <h1 class="m-display" style="font-size: clamp(1.75rem, 3vw, 2.5rem); margin-top: var(--m-space-2);">
+                    @_detail.Item.EventTitle
+                </h1>
+                <div class="m-mono" style="margin-top: var(--m-space-2); color: var(--m-c-ink-soft); text-transform: uppercase; letter-spacing: 0.14em; font-size: 0.75rem;">
+                    @L["Anomaly.Card.DetectedAt"] @_detail.Item.DetectedAt.ToString("dd MMM yyyy · HH:mm:ss") · MSK
+                </div>
+            </div>
+            <aside class="m-detail-header__odds">
+                <div class="m-detail-header__odds-row">
+                    <span class="m-detail-header__odds-label">@L["Anomaly.Card.Score"]</span>
+                    <SeverityBadge Severity="_detail.Item.Severity" Score="_detail.Item.Score" />
+                </div>
+                <div class="m-detail-header__odds-row">
+                    <span class="m-detail-header__odds-label">@L["Anomaly.Card.GapSeconds"]</span>
+                    <span class="m-mono" data-test="suspension-duration">@FormatGap(_detail.Item.SuspensionGapSeconds)</span>
+                </div>
+                <MudButton Variant="Variant.Outlined"
+                           StartIcon="@Icons.Material.Outlined.OpenInNew"
+                           OnClick="@(() => Nav.NavigateTo($"/events/{Uri.EscapeDataString(_detail.Item.EventId.Value)}"))"
+                           Class="m-detail-header__export"
+                           data-test="link-back-to-event">
+                    @L["Anomaly.Detail.LinkBackToEvent"]
+                </MudButton>
+            </aside>
+        </header>
+
+        <hr class="m-rule" />
+
+        <article class="m-card m-card--anomaly m-rise m-rise-2">
+            <span class="m-kicker" style="color: var(--m-c-anomaly); border-color: var(--m-c-anomaly);">
+                @L["Anomaly.Detail.EvidenceTitle"]
+            </span>
+            <div style="margin-top: var(--m-space-4);">
+                <AnomalyEvidence Pre="_detail.Pre"
+                                 Post="_detail.Post"
+                                 SuspensionGapSeconds="_detail.Item.SuspensionGapSeconds"
+                                 IsTwoWay="_detail.Item.IsTwoWay" />
+            </div>
+        </article>
+    }
+</section>
+
+@code {
+    [Parameter] public Guid Id { get; set; }
+
+    private AnomalyDetailVm? _detail;
+    private bool _loading = true;
+
+    protected override async Task OnParametersSetAsync()
+    {
+        _loading = true;
+        try
+        {
+            _detail = await Anomalies.GetByIdAsync(Id, CancellationToken.None);
+        }
+        catch
+        {
+            _detail = null;
+        }
+        finally
+        {
+            _loading = false;
+        }
+    }
+
+    private string KindLabel(AnomalyKind kind) => kind switch
+    {
+        AnomalyKind.SuspensionFlip => L["Anomaly.Kind.SuspensionFlip"],
+        _                          => kind.ToString(),
+    };
+
+    private static string FormatGap(int seconds)
+    {
+        if (seconds <= 0) return "—";
+        var ts = TimeSpan.FromSeconds(seconds);
+        if (ts.TotalSeconds < 60) return string.Format(System.Globalization.CultureInfo.InvariantCulture, "{0}s", (int)ts.TotalSeconds);
+        if (ts.TotalMinutes < 60) return string.Format(System.Globalization.CultureInfo.InvariantCulture, "{0}m {1:00}s", (int)ts.TotalMinutes, ts.Seconds);
+        return string.Format(System.Globalization.CultureInfo.InvariantCulture, "{0}h {1:00}m", (int)ts.TotalHours, ts.Minutes);
+    }
+}