feat: preview Team workspace in Desktop

[KillerQueen-Z]

Summary

• add a Personal / Team Beta workspace switch in Franklin Desktop
• introduce a Team home preview for shared conversations, files, knowledge, and workflows
• label all cloud-backed capabilities Coming soon and state that this beta uploads nothing
• preserve existing Personal conversations and navigation

Scope

This PR is an interface-only preview. It does not enable team cloud storage, permissions, member invites, shared wallets, or remote agent execution.

Verification

• full test suite: 653 passed
• Desktop typecheck passed
• Desktop lint passed
• production Desktop build passed
• packaged macOS app manually verified for Team entry and return to Personal