"""Pairing: token generation/verification + device registry.

Token generation (64-hex) and constant-time verification. Device registry
(SQLite) tracks ``device_id``, name, caps, fcm_token, ntfy_topic, last_seen,
created. QR payload for the pairing flow (``interactive_setup``).

Storage: ``get_hermes_home()/"android"/devices.db``.

Milestone M1.
"""