Dashboard: fix 500 on / from duplicate endpoint mapping

GatewayApplication.MapGatewayEndpoints registered MapGet("/", ...)
that redirected to /health/live. After the dashboard added a Blazor
component at @page "/", both endpoints matched GET / and the matcher
threw AmbiguousMatchException, surfacing as a 500. The redirect
predated the dashboard home page — drop it so / lands on Overview.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ZB.MOM.WW.MxGateway.Server/GatewayApplication.cs

@@ -136,8 +136,6 @@ public static class GatewayApplication
     {
         endpoints.MapStaticAssets(ResolveStaticAssetsManifestPath());
 
-        endpoints.MapGet("/", () => Results.Redirect("/health/live"));
-
         endpoints.MapGet(
                 "/health/live",
                 () => Results.Ok(new GatewayHealthReply(