Add interactive confirmation before cache clean

[ulises-jeremias]

Feature Request

Add an interactive confirmation prompt before cpa cache clean removes all cached entries, to prevent accidental data loss when running in a TTY.

Current behavior

cpa cache clean removes all entries immediately without asking.

Expected behavior

When running in a TTY, cpa cache clean should prompt: "Are you sure you want to remove all cached entries?" with Yes/No. In non-TTY mode, proceed without prompting.

Reference

CNA implements this safety prompt via an isTTY guard. Parity gap documented in the feature alignment sweep.