Backport HACS client foundation

[Wheemer]

Summary

This PR backports the current X-Sense client foundation from the HACS integration into python-xsense so the shared library can catch up with the integration behavior without carrying Home Assistant platform code.

Included

• Async authentication/session helpers and APK-aligned request handling.
• AWS shadow reads/writes, MQTT helper behavior, and normalized station/device/entity parsing.
• Camera discovery, option detail, history, recording, and WebRTC helper coverage used by the HA integration.
• Child-device identity alias handling for payloads that use devSerialNumber, serialNumber, sn, or related aliases.
• XS01-M isAlarm child payload normalization to alarmStatus.
• SBS50/SWS51 child-info shadow reads and compact field parsing.
• Legacy self-test action compatibility for supported devices.
• WebRTC client ICE candidates are now held until the camera SDP answer is received, matching the working HA camera signaling path.

Boundary

This intentionally does not move HA-specific platform/entity/config/frontend/blueprint code into the package. Those pieces stay in the Home Assistant integration layer.

Validation

• Python 3.10: 126 passed
• Python 3.11: 126 passed
• Python 3.12: 126 passed
• Python 3.13: 126 passed
• Python 3.14/main venv: 126 passed
• python -m build passed
• twine check dist\python_xsense-0.1.0* passed
• Fresh wheel install/import smoke test passed
• pip check passed