Apply technical-light design system to the gateway dashboard

Restyles the Blazor dashboard onto a portable token-based theme so it
reads like an instrument panel: warm-paper background, hairline-ruled
panels, IBM Plex type, monospace tabular numerics, and status carried by
colour chips. Vendors theme.css + IBM Plex fonts, rewrites dashboard.css
as a thin token-driven view layer, and swaps the Bootstrap navbar and
status badges for the design-system app bar and chips.

Also includes pending API-key management, Galaxy hierarchy projection,
and constraint-enforcement work with their tests.

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

src/MxGateway.Server/Dashboard/DashboardApiKeyAuthorization.cs

@@ -0,0 +1,22 @@
+using System.Security.Claims;
+using Microsoft.Extensions.Options;
+using MxGateway.Server.Configuration;
+
+namespace MxGateway.Server.Dashboard;
+
+public sealed class DashboardApiKeyAuthorization(IOptions<GatewayOptions> options)
+{
+    public bool CanManage(ClaimsPrincipal user)
+    {
+        if (user.Identity?.IsAuthenticated != true)
+        {
+            return false;
+        }
+
+        string requiredGroup = options.Value.Ldap.RequiredGroup;
+        IEnumerable<string> groups = user.FindAll(DashboardAuthenticationDefaults.LdapGroupClaimType)
+            .Select(claim => claim.Value);
+
+        return DashboardAuthenticator.IsMemberOfRequiredGroup(groups, requiredGroup);
+    }
+}