Heartless Hive

Refactor PolarBLE into core and app

This commit splits the project into a Windows app layer and a reusable net8.0 core for PMD decoding, sample timing, and LSL streaming. It adds robust ECG/accelerometer frame parsing, control-point handling, battery/throughput monitoring, and clean connect/disconnect teardown to prevent stale streams. The repo also adds project-level build/test configuration, CI packaging, and a focused xUnit suite covering the protocol and timing logic.