AI: Central SiteMap controls released vs in-development pages

- New SiteMap registry: single source of truth for page visibility.
  Fail-closed: unlisted or Released=false pages are hidden.
- NavMenu renders nav links from SiteMap.NavEntries (galaxy only).
- New Components/ReleaseGuard wraps the Router's Found template:
  unreleased routes redirect to /galaxy (covers direct URLs).
- Galaxy map released; system/mastery detail dossiers released but
  not in nav (linked from the map); Home, indexes, Units hidden.
- Brand logo now links to /galaxy.

ZeroSpace/ZeroSpace.Web/Components/ReleaseGuard.razor

@@ -0,0 +1,23 @@
+@inject NavigationManager Navigation
+
+@* Route guard: unreleased pages (see SiteMap) bounce to the galaxy map. *@
+@if (_released)
+{
+    <RouteView RouteData="@RouteData" DefaultLayout="@typeof(MainLayout)"/>
+}
+
+@code {
+    [Parameter, EditorRequired]
+    public RouteData RouteData { get; set; } = default!;
+
+    private bool _released;
+
+    protected override void OnInitialized()
+    {
+        _released = SiteMap.IsReleased(RouteData.PageType);
+        if (!_released)
+        {
+            Navigation.NavigateTo("/galaxy", replace: true);
+        }
+    }
+}