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/it.json

@@ -1700,7 +1700,6 @@
   "Thermal": "Termico",
   "Anime": "Anime",
   "Noir": "Noir",
-  "Snow": "Neve",
   "Current cockpit vision style: {style}. Activate for next style.": "Stile di visione attuale del cockpit: {style}. Attiva per lo stile successivo.",
   "Current style: {style} — click for next": "Stile attuale: {style}. Clic per il successivo",
   "Collapse Contact panel": "Comprimi il pannello Contatto",
@@ -2781,7 +2780,6 @@
   "Simulate FLIR-style thermal contrast. Turn up Ironbow for color.": "Simula il contrasto termico in stile FLIR. Alza Ironbow per il colore.",
   "Apply bright cel-shaded color and illustrated outlines.": "Applica colori vivaci cel-shaded e contorni illustrati.",
   "Apply high-contrast monochrome film-noir grading.": "Applica un color grading noir monocromatico ad alto contrasto.",
-  "Add a cold, snowy whiteout treatment to the scene.": "Aggiungi alla scena un effetto freddo di nevicata e whiteout.",
   "MAP SOURCE": "FONTE MAPPA",
   "Map source": "Fonte mappa",
   "Style": "Stile",