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.

CLAUDE.md

@@ -182,3 +182,24 @@ For full detail see `spike/SCRAPE_FINDINGS.md` and `spike/SCHEMA_DRAFT.md`.)
   `1st_Half`/`1st_Quarter`, tennis=`1st_Set`, hockey=`1st_Period`. Domain stores
   `PeriodNumber:int` and a sport-aware `PeriodScopeMapper` resolves the correct
   market token at parse time.
+
+## Feature: Initial Implementation > Phase 7: Anomaly UI — Learnings
+
+- **Severity buckets are a single-source rule** in
+  `Marathon.UI.Services.AnomalySeverityRules.FromScore` (Low <0.45, Medium <0.60,
+  High ≥0.60). The badge pill, card border, feed filter chip, and stat strip all
+  bind through it — never duplicate the thresholds.
+- **`AnomalyBrowsingService` is Scoped, `AnomalyBrowsingState` is Singleton** —
+  same lifetime split as `EventBrowsingService` / `EventBrowsingState`. State
+  holds the immutable `AnomalyFilter` + `LastSeenUtc` + cached unread count.
+- **`Anomaly.EvidenceJson` is parsed once in the service layer** via
+  `JsonSerializer.Deserialize<EvidenceDto>(json, PropertyNameCaseInsensitive=true)`
+  with private nested DTOs. Pages bind to `AnomalyEvidenceSnapshot` value-records
+  — they never see the raw JSON. Malformed JSON is dropped silently from the feed.
+- **2-way markets (tennis) carry `pDraw=null` / `rateDraw=null`.** The
+  `AnomalyEvidence` and `AnomalyCard` components key off the `IsTwoWay` flag on
+  `AnomalyListItem` (computed when both pre/post `pDraw` are null) to omit the
+  Draw row in BOTH columns — never per-column-individually.
+- **Signal-red is the load-bearing alert tone** for Phase 7. Use
+  `var(--m-c-anomaly)` exclusively (never raw `#dc2626`). Pulsing animation
+  (`m-pulse`) MUST respect `prefers-reduced-motion`.