Complete multilanguage support (French) with automatic translation infrastructure

[datamoc]

Summary

This PR implements complete multilanguage support for Wealthfolio with French as the first additional language. It includes comprehensive translation infrastructure, all UI translations, and proper internationalization throughout the application.

Key Features

Translation Infrastructure

• i18next integration with react-i18next
• 9 translation namespaces for organized translations
• Automatic language detection from OS/browser
• Language selector in Settings with "Auto (detect from system)" option
• Proper pluralization using i18next built-in features
• Single curly brace interpolation {variable} configured

Complete Translation Coverage

All Pages Translated:

• Navigation & Sidebar
• Dashboard (accounts summary, goals, performance)
• Holdings (table, charts, insights)
• Activities (table, import workflow, forms)
• Performance (metrics, charts)
• Accounts (management, forms)
• Income (dividend/interest tracking)
• Settings (all sections: general, accounts, goals, limits, market data, addons, exports, about)

UI Components Translated:

• DataTable component (search, reset, columns, no results)
• Currency names (automatic translation via Intl.DisplayNames API)
• Empty states and loading messages
• Toast notifications
• Form validation messages
• Error messages

French Typography

• Narrow non-breaking spaces (U+202F) before ! ? : ; (proper French typography)
• Proper accent marks and special characters

Translation Statistics

• Translation files: 18 JSON files (9 namespaces × 2 languages)
• Total translation keys: 900+ across all namespaces
• French completion: 100%
• Components updated: 50+ React components

[afadil]

Sorry, I will delay the i18n implementation. The app is still evolving rapidly with significant refactoring and changes, so it's not yet the right time to maintain an i18n system.