The key insight from go-proton-api SaltForKey: ProtonMail uses only the
last 31 chars of the bcrypt output as the key passphrase — not the full
60-char string. One line fix, two days of debugging.
Also adds the full crypto layer (crypto.rs): user key unlock, address key
token decryption, and message body decryption via rpgp. Includes SRP auth,
session caching with locked-scope handling, TOTP, and the ProtonMail API
client for inbox listing and message fetch.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
70b2b0348e