Implement first interactive TUI dashboard slice

[rmanibus]

Summary

Implement the first usable slice of the TUI dashboard described in RFC 0012 / #132.

Scope

• add a new cloudstic tui command
• render a full-screen terminal dashboard for profiles, stores, and auth
• show a summary overview plus a selectable profile list
• show details for the selected profile
• show an in-TUI activity panel instead of printing action output below the UI
• support keyboard navigation with arrow keys
• support terminal resize handling
• run in the alternate screen buffer for a proper full-screen TUI session
• provide a context-sensitive action to initialize a repository or run a backup for the selected profile

Notes

This issue tracks the initial interactive dashboard slice implemented by PR #212.

Follow-up interaction work can be tracked in separate issues after this lands.

Related

• RFC 0012 / RFC 0012: Epic / Tracking issue for interactive TUI mode #132
• PR Add first interactive TUI dashboard slice #212