uBix Vault v0.2.0-beta.6

Sixth beta. Human login and certificate management from the console.

Added

• userpass auth method — log in with a username and password (POST /v1/auth/userpass/login/{username}) → a token with the user's policies. Passwords stored only as a PBKDF2-HMAC-SHA256 hash (600k iterations, per-user salt) via the Go 1.24 stdlib crypto/pbkdf2 — no new dependency; constant-time compare, timing equalized for unknown users.
• PKI in the web console — the /ui/ console gains a PKI panel: generate/view the root CA, manage roles, and issue certificates (copy-able cert/key/CA, "shown once" key).

Pre-release. Not production-hardened; no external security review. For production, use HashiCorp Vault or OpenBao.

See CHANGELOG.md.