BREAKING CHANGE (forward-only): New credentials/keys encrypted with v2
(Argon2id-derived AES-256-GCM). Existing v1 records decrypt transparently.
- Argon2id params: 64 MiB memory, 3 iterations, 4 parallelism (OWASP)
- Per-record 16-byte salt stored in ciphertext format
- v2 format: v2:<salt>:<iv>:<authTag>:<ciphertext>
- Backwards compatible: v1 records still decrypt with raw key
- Admin endpoint POST /api/credentials/migrate-v2 upgrades all v1→v2
- Added docs/FUTURE-FEATURES.md with remaining spec gaps
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
