feat(ui/deployment): consolidate sites/areas/instances into Topology page

Single /deployment/topology page replaces /deployment/instances (legacy URL
preserved as a secondary @page directive) and the /admin/areas* CRUD pages.
TreeView with Site → Area → Instance, V1–V7 visual guide (bi-building /
bi-diagram-3 / bi-box), always-visible empty containers, search dim, F2
inline area rename, and right-click context menus per node kind (Add Area,
Move to Area…, lifecycle actions, etc.).

Adds AreaService.MoveAreaAsync with cycle prevention, same-site enforcement,
and name-collision check at the new parent. Instance rename intentionally
out of scope — UniqueName is the site-side actor identity, requires its own
design pass.

src/ScadaLink.CentralUI/Components/Layout/NavMenu.razor

@@ -42,9 +42,6 @@
                         <li class="nav-item">
                             <NavLink class="nav-link" href="/design/external-systems">External Systems</NavLink>
                         </li>
-                        <li class="nav-item">
-                            <NavLink class="nav-link" href="/admin/areas">Areas</NavLink>
-                        </li>
                     </Authorized>
                 </AuthorizeView>
 
@@ -53,7 +50,7 @@
                     <Authorized Context="deploymentContext">
                         <li class="nav-section-header">Deployment</li>
                         <li class="nav-item">
-                            <NavLink class="nav-link" href="/deployment/instances">Instances</NavLink>
+                            <NavLink class="nav-link" href="/deployment/topology">Topology</NavLink>
                         </li>
                         <li class="nav-item">
                             <NavLink class="nav-link" href="/deployment/deployments">Deployments</NavLink>