Give Avatar initials, person-mark, and load-error fallbacks so missing photos still look like the design-system atom.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/components/asset/Avatar/index.tsx

@@ -1,2 +1,7 @@
 export { default } from "./Avatar";
-export type { AvatarSizeValue } from "./Avatar";
+export type { AvatarProps } from "./Avatar";
+export type {
+  AvatarShapeValue,
+  AvatarSizeValue,
+  AvatarVariantValue,
+} from "./Avatar";