fix(ui): invariant decimals + LocaleState test isolation + drawer offset + bundled Plotly

Cross-cutting polish that surfaced while Phase 8 was being implemented:

* Invariant-culture formatting on every decimal ToString("0.00" / "0.##")
  (OddsCell, OddsTimeline, SeverityBadge, AnomalyEvidence,
  Pages/Events/Detail) — previously the comma/dot decimal separator
  switched with the locale and broke tabular alignment + tests.

* LocaleState constructor no longer mutates process-wide ambient culture;
  apply only happens through Set(...). Stops parallel bUnit test runs
  leaking ru-RU into each other's threads.

* MainLayout: drawer-open state now offsets main content / footer / appbar
  by the drawer width (248px) so the sidebar no longer overlaps content.
  Mobile breakpoint (≤720px) keeps the original full-width layout.

* wwwroot/index.html (Marathon.UI RCL): switched from Plotly CDN to the
  bundled "_content/Plotly.Blazor/plotly-2.35.3.min.js" — works offline
  and matches the Plotly.Blazor 5.4.1 version pin.

* Marathon.Hosts.WpfBlazor/wwwroot/index.html: host-level page that
  BlazorWebView's HostPage attribute resolves to. Same Plotly bundle,
  no autostart="false" (BlazorWebView auto-starts).

src/Marathon.UI/Components/AnomalyEvidence.razor

@@ -217,7 +217,7 @@
 
         builder.OpenElement(12, "span");
         builder.AddAttribute(13, "class", "m-evidence__rate");
-        builder.AddContent(14, rate is { } r ? r.ToString("0.00") : "—");
+        builder.AddContent(14, rate is { } r ? r.ToString("0.00", System.Globalization.CultureInfo.InvariantCulture) : "—");
         builder.CloseElement();
 
         builder.CloseElement();

src/Marathon.UI/Components/OddsCell.razor

@@ -87,7 +87,9 @@
     [Parameter] public string AriaPrefix { get; set; } = "Odds";
     [Parameter] public string EmptyPlaceholder { get; set; } = "—";
 
-    private string Formatted => Rate is { } r ? r.ToString("0.00") : EmptyPlaceholder;
+    private string Formatted => Rate is { } r
+        ? r.ToString("0.00", System.Globalization.CultureInfo.InvariantCulture)
+        : EmptyPlaceholder;
 
     private Trend Direction
     {

src/Marathon.UI/Components/OddsTimeline.razor

@@ -238,5 +238,6 @@
         },
     };
 
-    private static string FormatRate(decimal? r) => r is { } v ? v.ToString("0.00") : "—";
+    private static string FormatRate(decimal? r) =>
+        r is { } v ? v.ToString("0.00", System.Globalization.CultureInfo.InvariantCulture) : "—";
 }

src/Marathon.UI/Components/SeverityBadge.razor

@@ -19,7 +19,7 @@
     <span class="m-severity__label">@Label</span>
     @if (ShowScore && Score is { } s)
     {
-        <span class="m-severity__score m-mono" aria-hidden="true">@s.ToString("0.00")</span>
+        <span class="m-severity__score m-mono" aria-hidden="true">@s.ToString("0.00", System.Globalization.CultureInfo.InvariantCulture)</span>
     }
 </span>