A user can create a space for their Bluesky backups directly from the backups app

[travis]

1. After a user has logged in to Storacha in the webapp, they should see a button that lets them create a new Space.
2. After clicking the "create new space" button, the user should be run through the same steps we run them through in the w3 CLI (though of course these will all need to be adapted for the web):
   a) first the user should pick a name for the space (https://github.com/storacha/upload-service/blob/main/packages/cli/space.js#L51)
   b) next the user should be given an opportunity to see and write down the private key for the space (https://github.com/storacha/upload-service/blob/main/packages/cli/space.js#L58)
   c) next the user should be given an opportunity to create a space recovery delegation on the Storacha service (https://github.com/storacha/upload-service/blob/88e99d02be8bdb74d7bf9cd81af9abe62b2cb457/packages/cli/space.js#L111-L116)
3. After running through space creation, the user should see their new space selected in the space picker dropdown

[kaf-lamed-beyt]

So, @travis... here's what i've got so far. I still have to make some more UI tweaks to the dialog.

Screencast.from.14-03-2025.20.12.10.webm

I'm going to start working on b soon. Once I'm set, I'll open a PR