feat: use service memory heap instead of sessionStorage

There's currently an 8KB limit for items that can be stored via the `sessionStorage` API. This is going to be limiting if we are storing larger content, eg: images.

Start by locating the browser extension code that uses the sessionStorage API and trace how the service memory heap is exposed. Check how larger content such as images is stored and retrieved. Done means storage no longer has the stated 8KB limitation for recorded content.

Written by the indexing model from the issue text.