Implements HuamiHrvSummarySampleProvider to compute HRV summary statistics
on-demand from per-minute HRV value samples. Calculates weekly averages,
last night values, baselines, and HRV status (LOW/UNBALANCED/BALANCED).
This enables full HRV dashboard and status screen functionality for devices
that only provide raw HRV measurements without pre-computed summaries.
- Created HuamiHrvSummarySampleProvider with computed summary logic
- Added getHrvSummarySampleProvider() override in HuamiCoordinator
- Computes 7-day rolling average, last-night stats, and 14-day baselines
- Works retroactively with existing historical HRV data