v0.5.0

Changed

• The controller now acts on real PV headroom: available = production − base_load
  (base_load = 20th-percentile of recent consumption over a 60-min window) instead of a fixed
  surplus + wp_nominal load-compensation. The heat pump is no longer held ON on grid power
  when it modulates below its nominal draw. Falls back to the previous (sun-gated) logic when
  no fresh inverter production is available; the fail-safe chain and the sun-gate are unchanged.
• The exporter publishes production_w in /state only while the inverter reading is fresh
  (dropped after ~90 s stale), so the controller never computes on a frozen value.

Added

• Gauges surplus_control_base_load_watts and surplus_control_available_basis
  (1 = production-based, 0 = nominal fallback).