openScale sync 0.6.2 release

• New Endurain sync backend.
• Two-way sync: import measurements from Health Connect, Wger and MQTT.
• Optional background sync every 6 hours.
• Health Connect syncs bone mass, lean mass and BMR, and starts export-only: it reads only when you turn on import.
• It now also explains what is written and read before asking for permission.
• A failed sync is retried automatically and no longer blocks later ones.
• Pick which openScale to sync with when several are installed.