SvxPortal auth drop-in

Endpoints:
- /svxportal/auth/login.php (POST JSON {user, pass})
- /svxportal/auth/signup.php (POST JSON {email, callsign?, pass})
- /svxportal/auth/verify.php (GET tid, token)
- /svxportal/auth/consent.php (POST JSON {consent:'necessary'|'all'})
- /svxportal/auth/logout.php

Redis schema:
- registry:svxlink:acct:<uuid> (HASH) includes admin_level 1..3
- registry:svxlink:acct_by_email:<email_lower> -> uuid
- registry:svxlink:call:<CALLSIGN_UPPER> -> uuid
- registry:svxlink:acct_calls:<uuid> (SET) callsigns
- registry:svxlink:node:<node_id> -> uuid
- registry:svxlink:acct_nodes:<uuid> (SET) nodes