This is a placeholder issue for an initial sprint to "users can create and use private channels".

Figma: https://www.figma.com/design/PVQ1Kjf6Cq8ng1czuVtvR8/Create-channels-for-specific-roles?node-id=838-9409&t=gb61QyjnTR1QjJUG-0

The key is the switch/slider on the channel creation step to create a private channel.

The feature was imagined for either adding users or roles. It sounds like skipping roles for now and just focusing on users is the most ergonomic, so we can do that. Use this design and omit the "Roles" area.

Note the use of a new sidebar area on desktop to help unify desktop and mobile designs.

Acceptance criteria:

1. Users can create private channels and invite others
2. Channels correspond to encrypted groups in local-first auth and are secure. Non-invited members cannot commpel access
3. Channels are only visible to (and channel names are only decryptable by) invited members.

Nice to have:

1. Users can add more people to private channels
2. Feature matches design