[ARMultimediait]

Adds Italiano to View → Interface language, and Italian formula entry alongside Spanish.

What changes

• Interface: crates/ui-egui/src/i18n/it.rs translates every key the other catalogs
  translate (971 entries, ~44% of the estimated strings), following Excel's Italian wording
  («Blocca riquadri», «Unisci e allinea al centro», «Formattazione condizionale»). it-* locale
  tags resolve to Italian, so Italian systems get it on first run.
• Formulas: FormulaLocale::It with Excel's Italian names for about fifty common functions
  (SOMMA, MEDIA, SE, CONTA.NUMERI, SOMMA.SE, SOMMA.PIÙ.SE, SE.ERRORE, CERCA.VERT,
  CERCA.X, INDICE, CONFRONTA, VERO/FALSO…), decimal comma, ; arguments. Italian help
  for the most common signatures; the rest falls back to the English help with ;.
• Locale plumbing: the boolean aliases, normalize, the parser's input flag and the help
  lookup were hardwired to Spanish; they now take the locale, so a third table is one match
  arm. Name matching folds non-ASCII letters (PIÙ / più). Spanish behaviour is unchanged.
• Fix: the title-bar AutoSave label and its tooltip were English literals in every language;
  they now go through Language::tr.
• Docs: formula-input.md, localization-parity.md, ROADMAP.md.

Stored formulas, XLSX import/export, engine commands and the control/API keep canonical English
syntax, as for Spanish.

Open question

Array constants use \ between columns, as the Spanish table does. I could not confirm from
public documentation which column separator Italian Excel uses, so this is worth a check by
someone with Italian Excel at hand.

Testing

• cargo xtask ci passes on Windows 11. On a Windows checkout with core.autocrlf=true,
  parity and keytips report their generated files as out of date only because Git checked
  them out with CRLF; regenerating them changes no content, and the gate then passes.
• New crates/formula/tests/italian_input.rs: aliases and separators, decimal commas and array
  backslashes, display round-trip, defined names taking precedence over aliases, and Spanish and
  Italian tables staying separate.
• The i18n test now requires an Italian entry for every Japanese key; locale-tag tests cover
  it-IT / it_CH.
• Checked in the running app: ribbon and title bar in Italian, =SE(VERO;SOMMA(1,5;2,25);0)
  typed in a cell stores =IF(TRUE,SUM(1.5,2.25),0) and the formula bar shows it back in Italian.

The translations were drafted with an AI coding assistant (Claude Code); a review by a native
Italian speaker is welcome.

🤖 Generated with Claude Code

[FredApps]

I'm not approving yet, for two reasons.

• Eight other open PRs add Italian: #743 and #1286 (both close #682), #713, #714 (formulas), #1176, #1319, #1473 and #1743. None has a review yet. Only one of these should merge. Could the maintainers pick the base, and the others then fold in what they have that it lacks? This PR has the formula locale and the locale plumbing, which most of the others do not.
• The AutoSave change is a separate fix: ribbon.rs:55 and ribbon.rs:62 now go through Language::tr for every language. Only it.rs:984 and pt.rs:951 have an entry for "AutoSave". The same label and tooltip stay English in Czech, German, Spanish, French, Korean, Russian, Serbian and Chinese, so the fix is only partly done. Please split it into its own PR with the entries for each language, or drop it here and keep this PR to Italian.

I'll look at the Italian entries and formula names again once the base PR is chosen.

Hosted CI has not built this head.