Resolves https://github.com/webrecorder/browsertrix/issues/1951
### Changes
- Shows date org was created in superadmin org list
- Visually differentiates unnamed org ID
- Adds "Admin" badge to app header to make current login more apparent
- Fixes logic to show "create org" dialog if there are no orgs in an
instance
- Refactors `btrix-home` to remove unused references to non-superadmin
org list
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Co-authored-by: Henry Wilkinson <henry@wilkinson.graphics>
