Add color correction postprocessing filter

New filter with color temperature (2000-10000K) and per-channel RGB
gain controls. Uses LUT-based processing for fast per-frame application.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/locales/ru.json

@@ -293,6 +293,7 @@
   "filters.pixelate": "Пикселизация",
   "filters.auto_crop": "Авто Обрезка",
   "filters.flip": "Отражение",
+  "filters.color_correction": "Цветокоррекция",
   "postprocessing.description_label": "Описание (необязательно):",
   "postprocessing.description_placeholder": "Опишите этот шаблон...",
   "postprocessing.created": "Шаблон успешно создан",