keys add: no non-interactive --yes; mnemonic always printed unless --no-backup

[baktun14]

Summary

Scripted bootstrap of a test key is awkward:

akt context keys add e2e --yes
# unknown flag: --yes

--no-backup suppresses the mnemonic print (good for CI once the key exists), but there is no --yes to skip confirmation prompts on overwrite / first add in some paths. Piping y works but is fragile.

Expected

• Accept --yes / -y for non-interactive key add (common cosmos CLI pattern).
• Document --no-backup prominently for CI so mnemonics never hit logs.

Environment

akt 0.0.4, non-Console E2E 2026-08-12.