feat: Add comprehensive internationalization (i18n) support

- Add multi-language support with i18next and react-i18next
- Implement user-selectable date format preferences (5 formats)
- Add time format preferences (12-hour/24-hour)
- Implement RTL (right-to-left) support for Arabic, Hebrew, Persian, Urdu
- Add first day of week preference
- Create LocalizationContext for managing i18n settings
- Add LocalizationSettings component to Settings page
- Include sample translations: English, Spanish, Arabic
- Configure 10 languages: en, es, fr, de, ar, he, zh, ja, pt, ru
- Add translation management documentation and Crowdin config
- Create date formatting utilities that respect user preferences
- Add RTL CSS styles for proper layout mirroring
- Update Settings and ThemeToggle components to use translations
- Add comprehensive documentation (implementation guide, quick reference, translation guide)

All user preferences are persisted to localStorage and apply throughout the app.

src/utils/DateFormatter.js

@@ -0,0 +1,83 @@
+import moment from 'moment'
+
+export const createDateFormatter = (
+  dateFormat,
+  timeFormat,
+  firstDayOfWeek,
+) => {
+  moment.updateLocale('en', {
+    week: {
+      dow: firstDayOfWeek,
+    },
+  })
+
+  return {
+    formatDate: (date, customFormat) => {
+      if (!date) return ''
+      return moment(date).format(customFormat || dateFormat)
+    },
+
+    formatDateTime: (date, customFormat) => {
+      if (!date) return ''
+      const format = customFormat || `${dateFormat} ${timeFormat}`
+      return moment(date).format(format)
+    },
+
+    formatTime: (date, customFormat) => {
+      if (!date) return ''
+      return moment(date).format(customFormat || timeFormat)
+    },
+
+    formatRelative: date => {
+      if (!date) return ''
+      return moment(date).fromNow()
+    },
+
+    formatCalendar: (date, opts) => {
+      if (!date) return ''
+      return moment(date).calendar(null, opts)
+    },
+
+    formatShortDate: date => {
+      if (!date) return ''
+      return moment(date).format('MMM D, YYYY')
+    },
+
+    formatLongDate: date => {
+      if (!date) return ''
+      return moment(date).format('MMMM D, YYYY')
+    },
+
+    isBefore: (date, compareDate) => {
+      return moment(date).isBefore(compareDate)
+    },
+
+    isAfter: (date, compareDate) => {
+      return moment(date).isAfter(compareDate)
+    },
+
+    diff: (date1, date2, unit) => {
+      return moment(date1).diff(moment(date2), unit)
+    },
+
+    add: (date, amount, unit) => {
+      return moment(date).add(amount, unit).toDate()
+    },
+
+    subtract: (date, amount, unit) => {
+      return moment(date).subtract(amount, unit).toDate()
+    },
+  }
+}
+
+export const useDateFormatter = () => {
+  if (typeof window === 'undefined') {
+    return createDateFormatter('MM/DD/YYYY', 'h:mm A', 0)
+  }
+
+  const dateFormat = localStorage.getItem('dateFormat') || 'MM/DD/YYYY'
+  const timeFormat = localStorage.getItem('timeFormat') || 'h:mm A'
+  const firstDayOfWeek = parseInt(localStorage.getItem('firstDayOfWeek') || '0')
+
+  return createDateFormatter(dateFormat, timeFormat, firstDayOfWeek)
+}