Replace deprecated CONCENTRATION_* constants (HA 2027.8)

[kasiom]

Describe the Bug / 描述问题

Xiaomi Home v0.4.7 imports legacy concentration unit constants deprecated in HA 2026.7 and scheduled for removal in HA 2027.8. The imports remain in the current main branch.

How to Reproduce / 复现步骤

1. Use Xiaomi Home v0.4.7 on HA 2026.8.2.
2. Restart Home Assistant.
3. Open Settings > System > Logs.

Expected Behavior / 预期结果

Use UnitOfDensity and UnitOfRatio without deprecation warnings.

Reproduce Time / 问题复现的时间点

2026-08-20 00:07:00

Home Assistant Logs / 系统日志

The deprecated constant CONCENTRATION_MILLIGRAMS_PER_CUBIC_METER was used from xiaomi_home. It will be removed in HA Core 2027.8. Use UnitOfDensity.MILLIGRAMS_PER_CUBIC_METER instead.

The deprecated constants CONCENTRATION_PARTS_PER_BILLION and CONCENTRATION_PARTS_PER_MILLION were used from xiaomi_home. They will be removed in HA Core 2027.8. Use UnitOfRatio.PARTS_PER_BILLION and UnitOfRatio.PARTS_PER_MILLION instead.

Log Timezone / 日志时区

Europe/Prague

Home Assistant Core Version / Home Assistant Core 版本

2026.8.2

Home Assistant Operation System Version / Home Assistant Operation System 版本

18.2

Xiaomi Home Integration Version / 米家集成版本

v0.4.7

Additional Context / 其他说明

Still present in main commit 1a5f890. Migration guide: https://developers.home-assistant.io/blog/2026/06/30/new-unit-enumerators/