Periodic heartbeat in the broadcaster

Added

• Periodic heartbeat in the broadcaster: every 5 minutes all tracked entities are refreshed and their current state re-broadcast (async_track_time_interval). Seldom-changing entities such as on/off switches stay within the receiver's stale-entity timeout, so received ghost switches no longer disappear after roughly the stale-timeout period. The subscription is cancelled on shutdown.

Fixed

• Ghost sensor availability and the ghost switch presence used to rely on state changes alone; a switch that kept its value for longer than the receiver stale_timeout_minutes (default 10) was removed. The broadcaster heartbeat keeps every tracked entity's last_seen fresh on the receiver side.

Full Changelog: 2.0.2...2.1.2