Remove the Snow visual preset

Snow is no longer offered anywhere a style can be chosen: the Visual
Presets tray, keyboard shortcut 7, the Cockpit vision carousel, and the
set_visual_style voice action. The shader and its labels go with it;
weather snowfall and the SNOW weather condition are unaffected.

Share links keep working. Snow's enum code (6) stays reserved, so a
compact or long-form link that names it opens on Normal and drops the
Snow shader parameters without reporting them as unknown. A Scene
Director shot saved with Snow plays on Normal too. Snow's frozen share
defaults matched Normal's apart from those parameters, so no other
setting in an old link changes meaning.

The legacy voice-schema pins restore Snow before hashing, so the
unchanged pins still prove nothing else moved; the complete Realtime
payload digest is re-derived.

src/i18n/locales/zh-CN.json

@@ -1624,7 +1624,6 @@
   "Thermal": "热成像",
   "Anime": "动漫",
   "Noir": "黑白",
-  "Snow": "雪景",
   "Current cockpit vision style: {style}. Activate for next style.": "当前座舱视觉样式：{style}。点击可切换到下一个样式。",
   "Current style: {style} — click for next": "当前样式：{style}——点击切换到下一个",
   "Collapse Contact panel": "收起目标面板",
@@ -2535,7 +2534,6 @@
   "Simulate FLIR-style thermal contrast. Turn up Ironbow for color.": "模拟 FLIR 风格的热成像对比。调高 Ironbow 可显示色彩。",
   "Apply bright cel-shaded color and illustrated outlines.": "应用明亮的赛璐珞色彩和插画轮廓线。",
   "Apply high-contrast monochrome film-noir grading.": "应用高对比度的黑白电影风格调色。",
-  "Add a cold, snowy whiteout treatment to the scene.": "为场景添加寒冷的暴雪白化效果。",
   "MAP SOURCE": "地图源",
   "Map source": "地图源",
   "Style": "样式",