fix(vacay): fix entitlement counter, year deletion, and year creation bugs

- toggleCompanyHoliday now calls loadStats() so the entitlement sidebar
  updates immediately when a vacation day is converted to a company holiday
- deleteYear now deletes vacay_user_years rows for the removed year,
  preventing stale entitlement data from persisting and re-appearing
  when the year is re-created
- deleteYear recalculates carry-over for year+1 when year N is deleted,
  using the new actual previous year as the source
- removeYear store action now calls loadStats() so the sidebar reflects
  the recalculated carry-over without requiring a page refresh
- Add prev-year button (+[<] 2026 [>]+) so users can add years going
  backwards after deleting a past year; add vacay.addPrevYear i18n key
  to all 13 supported languages

Closes #371

client/src/i18n/translations/br.ts

@@ -579,7 +579,8 @@ const br: Record<string, string | { name: string; category: string }[]> = {
   'vacay.subtitle': 'Planeje e gerencie dias de férias',
   'vacay.settings': 'Configurações',
   'vacay.year': 'Ano',
-  'vacay.addYear': 'Adicionar ano',
+  'vacay.addYear': 'Adicionar próximo ano',
+  'vacay.addPrevYear': 'Adicionar ano anterior',
   'vacay.removeYear': 'Remover ano',
   'vacay.removeYearConfirm': 'Remover {year}?',
   'vacay.removeYearHint': 'Todas as entradas de férias e feriados da empresa deste ano serão excluídas permanentemente.',