feat(files): refactor thumbnails to lazy load

[josephmcg]

What this PR does 📖

• if thumbnail can be created, upload to ipfs as a separate file. previously, we were storing base64 thumbnail inside the index. They would typically max out at a few kb, but this makes the index much more lightweight. It wasn't scalable before
• on delete, unpin both file and thumbnail (need to confirm this actually works, left todo)
• on mount, pull thumbnail blob and create object url for display
  • revoke object url beforeDestroy to avoid memory leaks
• add background color for blurred nsfw images, they were slightly translucent before
• removed jsdoc from self explanatory computed
• minor refactoring around upload logic to make it reusable for thumbnails

Which issue(s) this PR fixes 🔨
AP-1877

Special notes for reviewers 🗒️

Additional comments 🎤