Fix compatibility with latest Home Assistant (2025) – async API and constants update

[Tloxipeuhca]

📖 Description

This Pull Request updates the Helios integration to ensure compatibility with the latest versions of Home Assistant.
🔹 Key Changes

API migration

    Replaced deprecated async_forward_entry_setup with the new async_forward_entry_setups method.

Constants update

    Replaced TEMP_CELSIUS with UnitOfTemperature.CELSIUS.

    Updated other outdated constants to align with current Home Assistant standards (SensorDeviceClass, UnitOfTemperature, etc.).

General compatibility improvements

    Cleaned up imports and removed deprecated references.

    Verified integration loads without errors on Home Assistant 2025.x.

🔹 Testing

Confirmed the integration loads successfully without errors in logs.

Verified entities (fan.helios, sensor.helios_boost_time, etc.) are created correctly.

Checked that services (helios.fan_boost, helios.stop_boost_mode) work as expected.

🔹 User Impact

Users can now install and run the Helios integration on the latest Home Assistant releases.

Improved stability and forward compatibility.