Add VLAN management page at /vlans

- Full CRUD: create, inline-edit, delete with confirm dialog
- Table shows VLAN ID, name, description, color swatch
- Add-VLAN form at top; hover shows edit/delete actions per row
- Route registered in App.tsx under ProtectedRoute
- VLANs nav button added to RackToolbar and MapToolbar

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/src/components/rack/RackToolbar.tsx

@@ -1,6 +1,6 @@
 import { useState } from 'react';
 import { useNavigate } from 'react-router-dom';
-import { Plus, Download, Map, LogOut } from 'lucide-react';
+import { Plus, Download, Map, LogOut, Tag } from 'lucide-react';
 import { toast } from 'sonner';
 import { toPng } from 'html-to-image';
 import { Button } from '../ui/Button';
@@ -64,6 +64,10 @@ export function RackToolbar({ rackCanvasRef }: RackToolbarProps) {
             <Map size={14} />
             Service Map
           </Button>
+          <Button size="sm" variant="secondary" onClick={() => navigate('/vlans')}>
+            <Tag size={14} />
+            VLANs
+          </Button>
           <Button size="sm" onClick={() => setAddRackOpen(true)}>
             <Plus size={14} />
             Add Rack