v0.4.5

Refresh panel on heater entity state change

• Panel watches the configured heater entity directly via set hass() (called by HA on every state update). When the entity transitions on↔off, panel triggers an immediate _refresh().
• Replaces the v0.4.4 event-bus subscription which relied on backend events being dispatched and required an HA restart to pick up; this approach reacts to the entity state itself.
• Closes the visible lag where toggling the heater externally still showed "STOP HEATING" until the next 5 s poll.