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.

public/locales/ar/chores.json

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+{
+  "title": "المهام",
+  "myChores": "مهامي",
+  "allChores": "جميع المهام",
+  "addChore": "إضافة مهمة",
+  "editChore": "تعديل مهمة",
+  "deleteChore": "حذف مهمة",
+  "completeChore": "إكمال مهمة",
+  "dueDate": "تاريخ الاستحقاق",
+  "assignedTo": "مُسند إلى",
+  "priority": "الأولوية",
+  "status": "الحالة",
+  "description": "الوصف"
+}

public/locales/ar/common.json

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+{
+  "save": "حفظ",
+  "cancel": "إلغاء",
+  "delete": "حذف",
+  "edit": "تعديل",
+  "close": "إغلاق",
+  "confirm": "تأكيد",
+  "loading": "جارٍ التحميل...",
+  "error": "خطأ",
+  "success": "نجح",
+  "warning": "تحذير",
+  "refresh": "تحديث",
+  "copy": "نسخ",
+  "copied": "تم النسخ!",
+  "settings": "الإعدادات",
+  "yes": "نعم",
+  "no": "لا"
+}

public/locales/ar/settings.json

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+{
+  "title": "الإعدادات",
+  "localization": {
+    "title": "التوطين",
+    "description": "تخصيص اللغة وتنسيق التاريخ والتفضيلات الإقليمية لحسابك.",
+    "language": "اللغة",
+    "languageDescription": "اختر لغتك المفضلة",
+    "dateFormat": "تنسيق التاريخ",
+    "dateFormatDescription": "اختر كيفية عرض التواريخ في التطبيق",
+    "timeFormat": "تنسيق الوقت",
+    "timeFormatDescription": "اختر تنسيق 12 أو 24 ساعة",
+    "12hour": "12 ساعة (ص/م)",
+    "24hour": "24 ساعة",
+    "firstDayOfWeek": "أول يوم في الأسبوع",
+    "firstDayOfWeekDescription": "اختر اليوم الذي يبدأ به أسبوعك",
+    "sunday": "الأحد",
+    "monday": "الاثنين",
+    "formats": {
+      "mdy": "MM/DD/YYYY (الولايات المتحدة)",
+      "dmy": "DD/MM/YYYY (أوروبا)",
+      "ymd": "YYYY-MM-DD (ISO)",
+      "long": "تنسيق طويل (مثل 1 يناير 2024)",
+      "short": "تنسيق قصير (مثل 1 يناير 2024)"
+    }
+  },
+  "theme": {
+    "title": "تفضيلات المظهر",
+    "description": "اختر كيف يبدو الموقع لك. حدد مظهرًا واحدًا أو قم بالمزامنة مع نظامك والتبديل تلقائيًا بين مظاهر النهار والليل.",
+    "themeMode": "وضع المظهر",
+    "light": "فاتح",
+    "dark": "داكن",
+    "system": "النظام"
+  }
+}

public/locales/en/chores.json

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+{
+  "title": "Chores",
+  "myChores": "My Chores",
+  "allChores": "All Chores",
+  "addChore": "Add Chore",
+  "editChore": "Edit Chore",
+  "deleteChore": "Delete Chore",
+  "completeChore": "Complete Chore",
+  "dueDate": "Due Date",
+  "assignedTo": "Assigned To",
+  "priority": "Priority",
+  "status": "Status",
+  "description": "Description"
+}

public/locales/en/common.json

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+{
+  "save": "Save",
+  "cancel": "Cancel",
+  "delete": "Delete",
+  "edit": "Edit",
+  "close": "Close",
+  "confirm": "Confirm",
+  "loading": "Loading...",
+  "error": "Error",
+  "success": "Success",
+  "warning": "Warning",
+  "refresh": "Refresh",
+  "copy": "Copy",
+  "copied": "Copied!",
+  "settings": "Settings",
+  "yes": "Yes",
+  "no": "No"
+}

public/locales/en/settings.json

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+{
+  "title": "Settings",
+  "circleSettings": {
+    "title": "Circle settings",
+    "description": "Your account is automatically connected to a Circle when you create or join one. Easily invite friends by sharing the unique Circle code or link below. You'll receive a notification below when someone requests to join your Circle. If you'd like to leave, simply hit the 'Leave Circle' button.",
+    "circleCode": "Circle Code",
+    "copyCode": "Copy Code",
+    "copyLink": "Copy Link",
+    "codeCopied": "Circle code copied!",
+    "linkCopied": "Circle link copied!",
+    "joinCircle": "Join a Circle",
+    "joinCirclePlaceholder": "Enter Circle Code",
+    "join": "Join",
+    "leave": "Leave Circle",
+    "leaveConfirmTitle": "Leave Circle",
+    "leaveConfirmMessage": "Are you sure you want to leave this circle?",
+    "circleMembers": "Circle Members",
+    "circleMemberRequests": "Circle Member Requests",
+    "admin": "Admin",
+    "member": "Member",
+    "pending": "Pending",
+    "accept": "Accept",
+    "reject": "Reject",
+    "makeAdmin": "Make Admin",
+    "makeMember": "Make Member",
+    "remove": "Remove",
+    "webhookURL": "Webhook URL",
+    "webhookDescription": "Enter a webhook URL to receive notifications for circle events",
+    "webhookPlaceholder": "https://your-webhook-url.com"
+  },
+  "accountSettings": {
+    "title": "Account Settings",
+    "subscription": "Subscription",
+    "subscriptionStatus": "Current Plan",
+    "free": "Free",
+    "plus": "Plus",
+    "upgrade": "Upgrade",
+    "cancel": "Cancel",
+    "changePassword": "Change Password",
+    "password": "Password",
+    "dangerZone": "Danger Zone",
+    "dangerZoneDescription": "Once you delete your account, there is no going back. Please be certain.",
+    "deleteAccount": "Delete Account"
+  },
+  "localization": {
+    "title": "Localization",
+    "description": "Customize language, date format, and regional preferences for your account.",
+    "language": "Language",
+    "languageDescription": "Select your preferred language",
+    "dateFormat": "Date Format",
+    "dateFormatDescription": "Choose how dates should be displayed throughout the application",
+    "timeFormat": "Time Format",
+    "timeFormatDescription": "Select 12-hour or 24-hour time format",
+    "12hour": "12-hour (AM/PM)",
+    "24hour": "24-hour",
+    "firstDayOfWeek": "First Day of Week",
+    "firstDayOfWeekDescription": "Select which day starts your week",
+    "sunday": "Sunday",
+    "monday": "Monday",
+    "formats": {
+      "mdy": "MM/DD/YYYY (US)",
+      "dmy": "DD/MM/YYYY (Europe)",
+      "ymd": "YYYY-MM-DD (ISO)",
+      "long": "Long format (e.g., January 1, 2024)",
+      "short": "Short format (e.g., Jan 1, 2024)"
+    }
+  },
+  "sidepanel": {
+    "title": "Sidepanel Customization",
+    "description": "Customize the layout and visibility of cards in the sidepanel. This section is only available on large screen devices such as tablets and desktops."
+  },
+  "theme": {
+    "title": "Theme preferences",
+    "description": "Choose how the site looks to you. Select a single theme, or sync with your system and automatically switch between day and night themes.",
+    "themeMode": "Theme mode",
+    "light": "Light",
+    "dark": "Dark",
+    "system": "System"
+  },
+  "notifications": {
+    "settingsSaved": "Settings saved successfully",
+    "settingsSaveFailed": "Failed to save settings",
+    "invalidWebhook": "Invalid webhook URL"
+  }
+}

public/locales/es/chores.json

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+{
+  "title": "Tareas",
+  "myChores": "Mis Tareas",
+  "allChores": "Todas las Tareas",
+  "addChore": "Agregar Tarea",
+  "editChore": "Editar Tarea",
+  "deleteChore": "Eliminar Tarea",
+  "completeChore": "Completar Tarea",
+  "dueDate": "Fecha de Vencimiento",
+  "assignedTo": "Asignado a",
+  "priority": "Prioridad",
+  "status": "Estado",
+  "description": "Descripción"
+}

public/locales/es/common.json

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+{
+  "save": "Guardar",
+  "cancel": "Cancelar",
+  "delete": "Eliminar",
+  "edit": "Editar",
+  "close": "Cerrar",
+  "confirm": "Confirmar",
+  "loading": "Cargando...",
+  "error": "Error",
+  "success": "Éxito",
+  "warning": "Advertencia",
+  "refresh": "Actualizar",
+  "copy": "Copiar",
+  "copied": "¡Copiado!",
+  "settings": "Configuración",
+  "yes": "Sí",
+  "no": "No"
+}

public/locales/es/settings.json

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+{
+  "title": "Configuración",
+  "circleSettings": {
+    "title": "Configuración del círculo",
+    "description": "Tu cuenta se conecta automáticamente a un Círculo cuando creas o te unes a uno. Invita fácilmente a amigos compartiendo el código único del Círculo o el enlace a continuación.",
+    "circleCode": "Código del Círculo",
+    "copyCode": "Copiar Código",
+    "copyLink": "Copiar Enlace",
+    "codeCopied": "¡Código del círculo copiado!",
+    "linkCopied": "¡Enlace copiado!",
+    "joinCircle": "Unirse a un Círculo",
+    "joinCirclePlaceholder": "Ingresa el Código del Círculo",
+    "join": "Unirse",
+    "leave": "Salir del Círculo",
+    "leaveConfirmTitle": "Salir del Círculo",
+    "leaveConfirmMessage": "¿Estás seguro de que quieres salir de este círculo?",
+    "circleMembers": "Miembros del Círculo",
+    "circleMemberRequests": "Solicitudes de Miembros del Círculo",
+    "admin": "Administrador",
+    "member": "Miembro",
+    "pending": "Pendiente",
+    "accept": "Aceptar",
+    "reject": "Rechazar",
+    "makeAdmin": "Hacer Administrador",
+    "makeMember": "Hacer Miembro",
+    "remove": "Eliminar",
+    "webhookURL": "URL del Webhook",
+    "webhookDescription": "Ingresa una URL de webhook para recibir notificaciones de eventos del círculo",
+    "webhookPlaceholder": "https://tu-url-webhook.com"
+  },
+  "accountSettings": {
+    "title": "Configuración de la Cuenta",
+    "subscription": "Suscripción",
+    "subscriptionStatus": "Plan Actual",
+    "free": "Gratis",
+    "plus": "Plus",
+    "upgrade": "Actualizar",
+    "cancel": "Cancelar",
+    "changePassword": "Cambiar Contraseña",
+    "password": "Contraseña",
+    "dangerZone": "Zona de Peligro",
+    "dangerZoneDescription": "Una vez que elimines tu cuenta, no hay vuelta atrás. Por favor, está seguro.",
+    "deleteAccount": "Eliminar Cuenta"
+  },
+  "localization": {
+    "title": "Localización",
+    "description": "Personaliza el idioma, formato de fecha y preferencias regionales para tu cuenta.",
+    "language": "Idioma",
+    "languageDescription": "Selecciona tu idioma preferido",
+    "dateFormat": "Formato de Fecha",
+    "dateFormatDescription": "Elige cómo se deben mostrar las fechas en toda la aplicación",
+    "timeFormat": "Formato de Hora",
+    "timeFormatDescription": "Selecciona formato de 12 o 24 horas",
+    "12hour": "12 horas (AM/PM)",
+    "24hour": "24 horas",
+    "firstDayOfWeek": "Primer Día de la Semana",
+    "firstDayOfWeekDescription": "Selecciona qué día comienza tu semana",
+    "sunday": "Domingo",
+    "monday": "Lunes",
+    "formats": {
+      "mdy": "MM/DD/AAAA (EE.UU.)",
+      "dmy": "DD/MM/AAAA (Europa)",
+      "ymd": "AAAA-MM-DD (ISO)",
+      "long": "Formato largo (ej., 1 de enero de 2024)",
+      "short": "Formato corto (ej., 1 ene 2024)"
+    }
+  },
+  "sidepanel": {
+    "title": "Personalización del Panel Lateral",
+    "description": "Personaliza el diseño y la visibilidad de las tarjetas en el panel lateral. Esta sección solo está disponible en dispositivos de pantalla grande como tabletas y computadoras de escritorio."
+  },
+  "theme": {
+    "title": "Preferencias de tema",
+    "description": "Elige cómo se ve el sitio para ti. Selecciona un solo tema o sincronízalo con tu sistema y cambia automáticamente entre temas de día y noche.",
+    "themeMode": "Modo de tema",
+    "light": "Claro",
+    "dark": "Oscuro",
+    "system": "Sistema"
+  },
+  "notifications": {
+    "settingsSaved": "Configuración guardada con éxito",
+    "settingsSaveFailed": "Error al guardar la configuración",
+    "invalidWebhook": "URL de webhook no válida"
+  }
+}