locale & i18n
Targeted by e2e/locale.spec.ts.
explicit locale="de" — German month + weekday names
custom_strings overrides only the Today button label
month_names override — uses numeric labels
week_start_day="0" — Sunday is first weekday column
week_start_day="1" — Monday is first weekday column
month-names attribute (pipe-delimited Czech) — June → "Červen"
weekday-names (Sunday-first Czech) + week_start_day="0" — first column "Ne"
weekday-names (Sunday-first) + week_start_day="3" — Wednesday-first, first column "St"
weekday-names with wrong segment count — ignored, falls back to locale (Su…)