feat: avatars for humans (#273)

* implement avatar backend functionality

* add avatar endpoints

* typo

* implement client side avatar upload and handling

* fixes

* Update go/internal/handler/handler.go

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* Update js/desktop/src/lib/avatar-image.ts

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

* bug in order

* remove unused component

* fix invalid migration

* fix syntax errors

---------

Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

js/desktop/src/hooks/use-avatar-url.ts

@@ -0,0 +1,20 @@
+import { useQuery, skipToken } from '@tanstack/react-query';
+import { apiClient } from '@/api/client';
+
+/**
+ * Resolves an avatar object id to a signed download URL. Mirrors
+ * {@link import('./use-download-url').useDownloadUrl} — React Query handles
+ * caching and de-duping, so many avatars sharing an id make a single request.
+ */
+export function useAvatarUrl(
+  objectId: string | null | undefined,
+): string | undefined {
+  const { data } = useQuery({
+    queryKey: ['avatar-url', objectId],
+    queryFn: objectId
+      ? () => apiClient.getAvatarDownloadUrl(objectId)
+      : skipToken,
+    staleTime: 1000 * 60 * 60, // 1 hour — signed URLs valid for 24h
+  });
+  return data;
+}