feat(documents): AggregatedSection + useAggregatedListing

Two TanStack Query hooks fetch the entity-aggregated payload for files
and workflows; AggregatedSection renders one labelled subsection per
owner-source group with a Show all (N) button wired via the onShowAll
callback. Dumb component — parent owns the row rendering + drill-
through navigation (Task 15 composes this into EntityFolderView).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/hooks/use-aggregated-listing.ts

@@ -0,0 +1,63 @@
+'use client';
+
+import { useQuery } from '@tanstack/react-query';
+
+import { apiFetch } from '@/lib/api/client';
+
+export interface AggregatedFile {
+  id: string;
+  filename: string;
+  mimeType: string | null;
+  createdAt: string;
+  folderId: string | null;
+  clientId: string | null;
+  companyId: string | null;
+  yachtId: string | null;
+}
+
+export interface AggregatedWorkflow {
+  id: string;
+  title: string;
+  status: string;
+  documentType: string;
+  updatedAt: string;
+  createdAt: string;
+}
+
+export interface AggregatedGroup<T> {
+  label: string;
+  source: 'direct' | 'client' | 'company' | 'yacht';
+  files?: T[];
+  workflows?: T[];
+  total: number;
+}
+
+export function useAggregatedFiles(
+  entityType: 'client' | 'company' | 'yacht' | undefined,
+  entityId: string | undefined,
+) {
+  return useQuery<AggregatedGroup<AggregatedFile>[]>({
+    queryKey: ['files', 'aggregated', entityType, entityId],
+    queryFn: () =>
+      apiFetch<{ data: { groups: AggregatedGroup<AggregatedFile>[] } }>(
+        `/api/v1/files?entityType=${entityType}&entityId=${entityId}`,
+      ).then((r) => r.data.groups),
+    enabled: Boolean(entityType && entityId),
+    staleTime: 10_000,
+  });
+}
+
+export function useAggregatedWorkflows(
+  entityType: 'client' | 'company' | 'yacht' | undefined,
+  entityId: string | undefined,
+) {
+  return useQuery<AggregatedGroup<AggregatedWorkflow>[]>({
+    queryKey: ['documents', 'aggregated', entityType, entityId],
+    queryFn: () =>
+      apiFetch<{ data: { groups: AggregatedGroup<AggregatedWorkflow>[] } }>(
+        `/api/v1/documents?entityType=${entityType}&entityId=${entityId}`,
+      ).then((r) => r.data.groups),
+    enabled: Boolean(entityType && entityId),
+    staleTime: 10_000,
+  });
+}