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/index.css

@@ -45,3 +45,44 @@ html {
 .animate-optimized.animation-complete {
   will-change: auto;
 }
+
+/* RTL Support */
+[dir='rtl'] {
+  direction: rtl;
+  text-align: right;
+}
+
+[dir='rtl'] .rtl-mirror {
+  transform: scaleX(-1);
+}
+
+/* Handle margins and paddings for RTL */
+[dir='rtl'] .ml-auto {
+  margin-left: 0;
+  margin-right: auto;
+}
+
+[dir='rtl'] .mr-auto {
+  margin-right: 0;
+  margin-left: auto;
+}
+
+/* Flip icons and arrows in RTL */
+[dir='rtl'] .rtl-flip {
+  transform: scaleX(-1);
+}
+
+/* Ensure proper text alignment in RTL */
+[dir='rtl'] input,
+[dir='rtl'] textarea {
+  text-align: right;
+}
+
+/* Handle border radius for RTL */
+[dir='rtl'] .rounded-l-none {
+  border-radius: 0 0.375rem 0.375rem 0;
+}
+
+[dir='rtl'] .rounded-r-none {
+  border-radius: 0.375rem 0 0 0.375rem;
+}