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/MainLayout.razor

@@ -83,6 +83,25 @@
         min-height: 0;
     }
 
+    /* MudDrawer is positioned fixed/absolute by Mud's CSS — push main content
+       right by the drawer's width (248px) so the sidebar doesn't overlap.
+       Same shift on the appbar tools row so the brand isn't covered. */
+    .m-app-frame.is-drawer-open .m-main,
+    .m-app-frame.is-drawer-open .m-footer {
+        padding-left: 248px;
+        transition: padding-left 200ms ease;
+    }
+    .m-app-frame.is-drawer-open .m-appbar {
+        padding-left: calc(248px + clamp(var(--m-space-3), 2vw, var(--m-space-5)));
+        transition: padding-left 200ms ease;
+    }
+    @@media (max-width: 720px) {
+        /* On narrow viewports the drawer becomes a temporary overlay anyway. */
+        .m-app-frame.is-drawer-open .m-main,
+        .m-app-frame.is-drawer-open .m-footer,
+        .m-app-frame.is-drawer-open .m-appbar { padding-left: 0; }
+    }
+
     .m-footer {
         display: flex;
         align-items: center;