feat(nodes): add High Availability management UI

Surface the existing HA backend endpoints (cluster HA status, add/remove
resource) in a new HAResources panel on the node detail page. Lists
HA-managed guests with state/group/restart limits, supports adding a guest
to HA (state, group, max_restart/relocate, comment) and removing it.
Shows a cluster-only notice on standalone nodes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/hooks/use-ha.ts

@@ -0,0 +1,51 @@
+import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
+import { apiClient } from '@/lib/api-client';
+import type { HAStatus } from '@/types';
+
+export const haKeys = {
+  status: (serverId: number) => ['ha-status', serverId] as const,
+};
+
+export interface AddToHAArgs {
+  vmType: 'vm' | 'ct';
+  vmid: number;
+  state: string;
+  group?: string;
+  max_restart: number;
+  max_relocate: number;
+  comment?: string;
+}
+
+export function useHAStatus(serverId: number) {
+  return useQuery({
+    queryKey: haKeys.status(serverId),
+    queryFn: () => apiClient.get<HAStatus>(`/proxmox/api/${serverId}/ha/status`),
+    enabled: serverId > 0,
+  });
+}
+
+export function useAddToHA(serverId: number) {
+  const qc = useQueryClient();
+  return useMutation({
+    // The backend expects these as query params, not a JSON body.
+    mutationFn: ({ vmType, vmid, state, group, max_restart, max_relocate, comment }: AddToHAArgs) => {
+      const qs = new URLSearchParams();
+      qs.set('state', state);
+      qs.set('max_restart', String(max_restart));
+      qs.set('max_relocate', String(max_relocate));
+      if (group) qs.set('group', group);
+      if (comment) qs.set('comment', comment);
+      return apiClient.post(`/proxmox/api/${serverId}/ha/${vmType}/${vmid}/add?${qs}`, {});
+    },
+    onSuccess: () => qc.invalidateQueries({ queryKey: haKeys.status(serverId) }),
+  });
+}
+
+export function useRemoveFromHA(serverId: number) {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: ({ vmType, vmid }: { vmType: 'vm' | 'ct'; vmid: number }) =>
+      apiClient.delete(`/proxmox/api/${serverId}/ha/${vmType}/${vmid}/remove`),
+    onSuccess: () => qc.invalidateQueries({ queryKey: haKeys.status(serverId) }),
+  });
+}