The web client calls auth/login to authenticate users, but this endpoint
was missing from the Hub API. Creates:
- api/hub/auth/login.php: password-based auth with token generation
- Hub_Users table: stores bcrypt password hashes and session tokens
- Auto-provisions on first login (creates credentials for existing agents)
- Adds route to PUBLIC_ROUTES in helpers.php
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
