refactor: Standardize localization config to simplify adding new languages

[O2sa]

Adding new languages currently requires updating multiple places. We should standardize the localization configuration into a single source of truth where each supported language defines its value, label, and layout direction (RTL/LTR).

Tasks

• Define a centralized LOCALES array (e.g., in lib/i18n.ts or a separate config file).
• Ensure each locale object includes a dir property ('ltr' or 'rtl').
• Update LanguageProvider and LanguageSwitcher to use this new configuration.
• Replace any hardcoded RTL logic (e.g., locale === 'ar') with the new dir property.
• Update CONTRIBUTING.md with a guide on how to add new languages and contribute to localization.> [!NOTE]

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