feat(i18n): add i18n module for localization support

- Introduce functions to initialize and load locale files dynamically
- Add support for translation keys with placeholder replacements
- Default to English if locale files are missing or not found
- Determine system language using environment variables

src/i18n/mod.ts

@@ -0,0 +1 @@
+export { getCurrentLanguage, initI18n, loadLocale, t } from './i18n.ts';