Tuya: expose backlight color/brightness for TS0601_dimmer_3

[kalitek999]

Summary

• Add backlight color + brightness exposes for TS0601_dimmer_3.
• Map DP 101 (backlight_color) and DP 103 (backlight_brightness).
• Add shared BacklightColorEnum in tuya lib.

Above changes allow to lower the brightness and set custom backlight color - very useful as default blue/white backlight is very bright at night - not comfortable in bedrooms.

Testing

• pnpm test

Device verification

• Tested via external converter on 3 gang dimmer: TS0601 _TZE204_znvwzxkq (Zemismart ZN2S‑RS3E‑DH).

Notes

• pnpm run check fails locally on Windows due to Biome schema mismatch/CRLF; ran pnpm dlx @biomejs/[email protected] on changed files only.

device page:
https://www.zigbee2mqtt.io/devices/ZN2S-RS3E-DH.html

[Koenkk]

Thanks!