feat: sortable resource tables and richer dashboard stack-health columns (#1498)

Make the Resources Images, Volumes, and Networks tables sortable with a
shared useTableSort hook and SortableTableHead, move the Images scan-history
control into the Images tab header, and keep the network List/Topology toggle
anchored with Create Network visible in both modes.

Rework the dashboard Stack health table: drop the redundant Host column, add
sortable Stack/Up/CPU/Mem headers, and add Source (local/git) and Port columns.
The status endpoint now labels each stack with its git/local source, computed
outside the cache so linking changes show immediately.

Extract a reusable CreateNetworkDialog and add a create-network action to the
stack-detail Networking tab.

frontend/src/components/ui/sortable-table.tsx

@@ -0,0 +1,30 @@
+import { ArrowUp, ArrowDown } from 'lucide-react';
+import { TableHead } from '@/components/ui/table';
+import { cn } from '@/lib/utils';
+import type { SortDir } from '@/hooks/useTableSort';
+
+/** Clickable, sort-aware `<TableHead>`. Pairs with the `useTableSort` hook. */
+export function SortableTableHead<K extends string>({
+  label, columnKey, activeKey, dir, onSort, className,
+}: {
+  label: string;
+  columnKey: K;
+  activeKey: K;
+  dir: SortDir;
+  onSort: (k: K) => void;
+  className?: string;
+}) {
+  const active = activeKey === columnKey;
+  return (
+    <TableHead className={cn('text-[11px] cursor-pointer select-none', className)}>
+      <button
+        type="button"
+        onClick={() => onSort(columnKey)}
+        className="inline-flex items-center gap-1 hover:text-foreground"
+      >
+        {label}
+        {active && (dir === 'asc' ? <ArrowUp className="w-3 h-3" /> : <ArrowDown className="w-3 h-3" />)}
+      </button>
+    </TableHead>
+  );
+}