Drop Snow from the new catalogs and migrate saved Snow shots

The it, pt and uk catalogs merged from main still carried the two Snow
button strings, which the catalog tests report as stale. They are
pruned with npm run i18n -- --prune.

A Scene Director shot saved with Snow now normalizes to Normal when the
project loads, so the shot list shows NORMAL rather than an untranslated
SNOW for a shot that plays on Normal. The README's style keys read 1-6.

src/i18n/locales/pt.json

@@ -1700,7 +1700,6 @@
   "Thermal": "Térmico",
   "Anime": "Anime",
   "Noir": "Noir",
-  "Snow": "Neve",
   "Current cockpit vision style: {style}. Activate for next style.": "Estilo atual de visão da cabine: {style}. Ative para o próximo estilo.",
   "Current style: {style} — click for next": "Estilo atual: {style} — clique para o próximo",
   "Collapse Contact panel": "Recolher painel de contato",
@@ -2783,7 +2782,6 @@
   "Simulate FLIR-style thermal contrast. Turn up Ironbow for color.": "Simular contraste térmico estilo FLIR. Aumente o Ironbow para ter cor.",
   "Apply bright cel-shaded color and illustrated outlines.": "Aplicar cores vivas em cel shading e contornos ilustrados.",
   "Apply high-contrast monochrome film-noir grading.": "Aplicar gradação monocromática de filme noir com alto contraste.",
-  "Add a cold, snowy whiteout treatment to the scene.": "Adicionar à cena um efeito frio de nevasca branca.",
   "MAP SOURCE": "FONTE DO MAPA",
   "Map source": "Fonte do mapa",
   "Style": "Estilo",