v2026.01.211

refactor: Decompose coordinator and add event-driven updates

Decompose Coordinator:
- Extract valve_manager.py: Valve control, anti-cycling, maintenance
- Extract heater_controller.py: Flow temperature calculation and control
- Extract zone_logic.py: Setpoint calculation and adaptive start utilities
- Coordinator reduced from 1387 to 1124 lines (~19% reduction)

Event-Driven Updates:
- Add state_debouncer.py: Debounced state change tracking
- Window sensor changes now trigger immediate zone updates (30s debounce)
- Added _update_single_zone for partial zone updates
- State debouncer properly cleans up listeners on shutdown

Changes:
- Module imports added to coordinator
- HeaterController and ValveManager instantiated in __init__
- StateDebouncer integrated with window sensor tracking
- async_shutdown updated to clean up debouncer listeners
- Service handler fixed for updated _perform_valve_maintenance signature

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>