Replace direct golang.org/x/term calls with mcdsl/terminal.ReadPassword
across mciasctl (6 sites), mciasgrpcctl (1 site), and mciasdb (1 site).
Aligns with the new CLI security standard in engineering-standards.md.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
