feat: lunar calendar support for countdowns

frontend/src/lib/mvp-utils.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest'
-import { countdownDayText, countdownKindLabel, dateKey, defaultView, habitWeek, isHabitComplete, isHabitScheduledToday, isTaskView, nextHabitSwipeValue, numericHabitInputValue, previousHabitSwipeValue, quickTaskFields, shouldToggleRowSwipe } from './mvp-utils'
+import { calendarModeLabel, countdownDayText, countdownKindLabel, dateKey, defaultView, habitWeek, isHabitComplete, isHabitScheduledToday, isTaskView, nextHabitSwipeValue, numericHabitInputValue, previousHabitSwipeValue, quickTaskFields, shouldToggleRowSwipe } from './mvp-utils'
 
 describe('MVP view utilities', () => {
   it('formats a local date as YYYY-MM-DD', () => {
@@ -70,6 +70,8 @@ describe('MVP view utilities', () => {
     expect(countdownKindLabel('countdown')).toBe('倒数日')
     expect(countdownKindLabel('anniversary')).toBe('纪念日')
     expect(countdownKindLabel('birthday')).toBe('生日')
+    expect(calendarModeLabel('solar')).toBe('公历')
+    expect(calendarModeLabel('lunar')).toBe('农历')
   })
 
   it('toggles a row for a deliberate mostly-horizontal swipe', () => {