- Replaced `SUPPORTED_LOCALES` with `supported_locales` for naming consistency.
- Applied formatting improvements to multiline statements for better readability.
- Cleaned up redundant comments and streamlined test assertions.
- Introduced `locale` field in user model and schemas with BCP 47 format validation.
- Created Alembic migration to add `locale` column to the `users` table with indexing for better query performance.
- Implemented `get_locale` dependency to detect locale using user preference, `Accept-Language` header, or default to English.
- Added extensive tests for locale validation, dependency logic, and fallback handling.
- Enhanced documentation and comments detailing the locale detection workflow and SUPPORTED_LOCALES configuration.
