feat(phase-6): event browsing UI — pre-match/live lists, detail page, +26 bUnit tests

Replaces PreMatch/Live placeholder pages with a shared EventListShell
(filter chips, date range, sortable virtualized-friendly table, debounced
search, live auto-refresh with odds-movement indicators) and adds a new
/events/{eventCode} detail page (asymmetric header lockup, dynamic
Match/Period tabs, Plotly.Blazor odds-over-time chart with accessible
data-table fallback, snapshot history, Excel export modal).

New primitives matching Phase 5's editorial-quant system:
- SportIcon: inline SVGs per sport (basketball=6, football=11,
  tennis=22723, hockey=43658, generic fallback)
- OddsCell: tabular mono with ▲/▼/— delta + flash on change
  (prefers-reduced-motion honored)
- OddsTimeline: Plotly.Blazor wrapper with theme-aware colors and
  <details>/<summary> data-table screen-reader fallback
- ExportDialog: From/To pickers + ExportKind radio + Esc/Enter
  keyboard, surfaces use-case errors inline
- EventListShell: shared section shell for PreMatch/Live cadence

State + service split keeps the RCL host-agnostic:
- IEventBrowsingService / EventBrowsingService — wraps repos, returns
  view-model records (EventListItem, EventDetail, EventScopeBoard,
  BetRow, OddsTimelinePoint, SnapshotHistoryEntry); pages never see
  EF or domain entities directly.
- EventBrowsingState — singleton (per-circuit in BlazorWebView) holding
  immutable PageFilter records for PreMatch and Live.

Plotly.Blazor 5.4.1 added (latest .NET 8 line; 7.x has breaking changes).
+59 RU/EN localization keys following the Phase 5 dot-segmented convention.

Tests: +26 bUnit tests (PreMatch/Live/Detail pages, OddsCell/SportIcon/
ExportDialog components, EventBrowsingState). Total 228/228 passing
(Domain 96 + Application 15 + Infrastructure 80 + UI 37; baseline 202).
Build clean (0/0).

PLAN.md: P2/P3/P5 top-level checkboxes ticked; P6 row marked Done.

tests/Marathon.UI.Tests/Support/MarathonTestContext.cs

@@ -19,6 +19,8 @@ public abstract class MarathonTestContext : TestContext
     protected TestSettingsWriter Writer { get; } = new();
     protected ThemeState Theme { get; } = new();
     protected LocaleState Locale { get; } = new();
+    protected EventBrowsingState BrowsingState { get; } = new();
+    protected FakeEventBrowsingService Browsing { get; } = new();
 
     protected MarathonTestContext()
     {
@@ -26,6 +28,8 @@ public abstract class MarathonTestContext : TestContext
         Services.AddSingleton<ISettingsWriter>(Writer);
         Services.AddSingleton(Theme);
         Services.AddSingleton(Locale);
+        Services.AddSingleton(BrowsingState);
+        Services.AddSingleton<IEventBrowsingService>(Browsing);
 
         Services.AddSingleton(typeof(IStringLocalizer<>), typeof(TestLocalizer<>));
         Services.AddSingleton(typeof(ILogger<>), typeof(NullLogger<>));