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/TestOptionsMonitor.cs

@@ -0,0 +1,41 @@
+using Microsoft.Extensions.Options;
+
+namespace Marathon.UI.Tests.Support;
+
+/// <summary>
+/// Minimal in-memory <see cref="IOptionsMonitor{TOptions}"/> for tests.
+/// </summary>
+public sealed class TestOptionsMonitor<T> : IOptionsMonitor<T> where T : class, new()
+{
+    private T _value;
+    private readonly List<Action<T, string?>> _listeners = new();
+
+    public TestOptionsMonitor(T initial)
+    {
+        _value = initial;
+    }
+
+    public T CurrentValue => _value;
+
+    public T Get(string? name) => _value;
+
+    public IDisposable OnChange(Action<T, string?> listener)
+    {
+        _listeners.Add(listener);
+        return new Subscription(() => _listeners.Remove(listener));
+    }
+
+    public void Set(T next)
+    {
+        _value = next;
+        foreach (var listener in _listeners.ToList())
+            listener(next, null);
+    }
+
+    private sealed class Subscription : IDisposable
+    {
+        private readonly Action _dispose;
+        public Subscription(Action dispose) { _dispose = dispose; }
+        public void Dispose() => _dispose();
+    }
+}