fix: resolve table column misalignment in flat list view

addresses #370 - changed from Show component to class-based hiding for the Node column to ensure proper table structure is maintained in both grouped and flat views. The Node column now always exists in the DOM but is hidden with CSS when not needed, preventing column shift issues.

frontend-modern/src/components/Dashboard/Dashboard.tsx

@@ -694,14 +694,12 @@ export function Dashboard(props: DashboardProps) {
                 >
                   VMID {sortKey() === 'vmid' && (sortDirection() === 'asc' ? '▲' : '▼')}
                 </th>
-                <Show when={groupingMode() === 'flat'}>
-                  <th 
-                    class="px-2 py-1.5 text-left text-[11px] sm:text-xs font-medium uppercase tracking-wider w-[100px] cursor-pointer hover:bg-gray-200 dark:hover:bg-gray-600"
-                    onClick={() => handleSort('node')}
-                  >
-                    Node {sortKey() === 'node' && (sortDirection() === 'asc' ? '▲' : '▼')}
-                  </th>
-                </Show>
+                <th 
+                  class={`px-2 py-1.5 text-left text-[11px] sm:text-xs font-medium uppercase tracking-wider w-[100px] cursor-pointer hover:bg-gray-200 dark:hover:bg-gray-600 ${groupingMode() === 'flat' ? '' : 'hidden'}`}
+                  onClick={() => handleSort('node')}
+                >
+                  Node {sortKey() === 'node' && (sortDirection() === 'asc' ? '▲' : '▼')}
+                </th>
                 <th 
                   class="px-2 py-1.5 text-left text-[11px] sm:text-xs font-medium uppercase tracking-wider w-[100px] cursor-pointer hover:bg-gray-200 dark:hover:bg-gray-600"
                   onClick={() => handleSort('uptime')}

frontend-modern/src/components/Dashboard/GuestRow.tsx

@@ -156,11 +156,9 @@ export function GuestRow(props: GuestRowProps) {
       </td>
 
       {/* Node (optional) */}
-      <Show when={props.showNode}>
-        <td class="p-1 px-2 text-sm text-gray-600 dark:text-gray-400">
-          {props.guest.node}
-        </td>
-      </Show>
+      <td class={`p-1 px-2 text-sm text-gray-600 dark:text-gray-400 ${props.showNode ? '' : 'hidden'}`}>
+        {props.guest.node}
+      </td>
 
       {/* Uptime */}
       <td class={`p-1 px-2 text-sm whitespace-nowrap ${