0.4.12

No breaking changes.

• session.py: fixed a thread-safety race between SHCPollingThread
  (sole mutator of _devices_by_id/_services_by_device_id) and cross-thread
  readers (devices property, device()) — a device add/remove racing a
  concurrent read could raise an unhandled RuntimeError: dictionary changed size during iteration in the reading thread. Added self._devices_lock
  (threading.RLock), held only for the actual dict mutation/snapshot —
  never across I/O (get_device_services) or subscriber-callback invocation,
  to avoid stalling readers/writers or risking deadlock. Found via a targeted
  bug-hunt round; not tied to a user report.