[Feature Request] Add de_CH locale or split de in de_{DE,AT,CH}

Description I would like to propose Swiss Standard German as a separate language on Crowdin and in the codebase. The currently available de locale corresponds to de-DE (Germany) and does not match Swiss conventions in a few important ways. Basics according to CONTRIBUTING.md: • English name: German (Switzerland) • ISO language code: de-CH • Date format: dd.mm.yyyy (e.g. 19.05.2026) Other Swiss Standard German (Schweizer Hochdeutsch) differs from the German used in Germany in several ways that are relevant here: • In Switzerland, ß is replaced with ss in all contexts (e.g. Strasse instead of Straße, grösser instead of größer). This can be handled in the translations on Crowdin once the locale is enabled. • Switzerland generally uses an apostrophe as the thousands separator and a dot as the decimal separator for currency amounts, e.g. 165’000.25 CHF ([Federal Chancellery style]( Unicode U+2019, sometimes written with a straight apostrophe). T…