Password hashing migrated from bcrypt to Argon2id (m=64MiB, t=3, p=4).
Transparent upgrade: on successful bcrypt login, re-hashes with Argon2id
and persists. New signups and password changes use Argon2id directly.
Unifies crypto stack — Argon2id was already used for TOTP and backup KDF.
Bitcoin RPC password: no longer falls back to hardcoded "archipelago123".
On first boot, generates a random 32-char hex password from CSPRNG,
saves to /var/lib/archipelago/secrets/bitcoin-rpc-password with 0600
permissions. Existing installs with secrets file are unaffected.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>