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/Services/EventBrowsingStateTests.cs

@@ -0,0 +1,51 @@
+using Marathon.UI.Services;
+
+namespace Marathon.UI.Tests.Services;
+
+public sealed class EventBrowsingStateTests
+{
+    [Fact]
+    public void Default_filter_spans_minus_one_to_plus_seven_days()
+    {
+        var state = new EventBrowsingState();
+        var f = state.PreMatch;
+        (f.To - f.From).TotalDays.Should().BeApproximately(8, 0.01);
+        f.SortKey.Should().Be(EventSortKey.ScheduledAt);
+        f.SortDescending.Should().BeFalse();
+    }
+
+    [Fact]
+    public void UpdatePreMatch_raises_OnChange_when_value_changes()
+    {
+        var state = new EventBrowsingState();
+        var fired = 0;
+        state.OnChange += () => fired++;
+
+        var next = state.PreMatch with { SearchTerm = "Real Madrid" };
+        state.UpdatePreMatch(next);
+
+        fired.Should().Be(1);
+        state.PreMatch.SearchTerm.Should().Be("Real Madrid");
+    }
+
+    [Fact]
+    public void UpdatePreMatch_does_not_raise_when_value_unchanged()
+    {
+        var state = new EventBrowsingState();
+        var fired = 0;
+        state.OnChange += () => fired++;
+
+        state.UpdatePreMatch(state.PreMatch with { });
+
+        fired.Should().Be(0);
+    }
+
+    [Fact]
+    public void Live_and_PreMatch_filters_are_independent()
+    {
+        var state = new EventBrowsingState();
+        state.UpdateLive(state.Live with { SearchTerm = "live-only" });
+        state.PreMatch.SearchTerm.Should().BeEmpty();
+        state.Live.SearchTerm.Should().Be("live-only");
+    }
+}