v2.6.1-beta.3

Added

• Cost sensor (EyeOnWaterCostSensor): new entity with device_class=MONETARY and state_class=TOTAL_INCREASING for tracking water cost in the Energy Dashboard
• Options flow: configure a static unit price (cost per unit of water) via integration settings
• Delta-based cost accumulation with RestoreEntity persistence across restarts
• 14 new test cases for cost sensor

Fixed

• Forward reference error in config_flow.py (added from __future__ import annotations)