* fix: web: Archived: Show displayTime instead of updateTime

Archiving a memo is considered "updating" it, so the time it was
archived will be displayed, instead of the time it was created.

* fix: web: Archived: Add an option to fetch more memos

Just like on other pages, add a button to fetch more memos. Otherwise,
the user would only be able to load the latest 10 memos, as defined in
DEFAULT_MEMO_LIMIT.