Local mode stability fixes

Fixes for local (LAN) mode:

• Fixed startup sometimes hanging indefinitely when the device was
  offline or slow to respond (socket lock now times out instead of
  blocking forever)
• Fixed occasional "No 'dps' in status response" errors caused by a
  duplicate first-refresh race
• Fixed select/switch/number values briefly flickering back to the
  old value after a change (now updates instantly, corrects itself
  if the device echoes a stale value)
• Fixed a bug where partial local updates could wipe out other
  entities' data
• Local reconnect attempts now back off gradually (5s→60s) instead
  of hammering an offline device forever

No model file changes needed — update coordinator.py only.