fix(web): small issues with the memory viewer. (#19184)

* Match fade transition timing between photo-viewer and memory-viewer.

* Fix blank page after refreshing memory page.

If the user refreshed in the browser while on the memory page, the page
would show a blank page. This was caused by skipping initialization in
afterNavigate. Fix by always initializing the memory page in
afterNavigate.

web/src/lib/constants.ts

@@ -420,3 +420,5 @@ export enum ToggleVisibility {
   HIDE_UNNANEMD = 'hide-unnamed',
   SHOW_ALL = 'show-all',
 }
+
+export const assetViewerFadeDuration: number = 150;