[TASK]Use standard language tags (BCP 47).

[Basartemiz]

Use Standard Language Tags (BCP 47)

📌 Description

To ensure proper internationalization (i18n) and compliance with standards, the platform must use BCP 47 language tags for all user-facing content and localization settings.
This will improve compatibility with translation tools, assistive technologies, and multilingual support across the system.

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✅ Acceptance Criteria

• All user-facing content is tagged with appropriate BCP 47 language codes (e.g., en-US, tr-TR).
• Database fields and API responses include language metadata when applicable.
• The frontend (React, React Native) uses BCP 47 tags for locale selection.
• Backend (Django REST Framework) enforces and validates language tags in requests and responses.
• Verified compliance with internationalization standards.

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📋 Tasks

• Audit current multilingual implementation (English/Turkish).
• Update frontend i18n libraries to store and serve languages using BCP 47 format.
• Configure backend to handle locale negotiation based on BCP 47 tags.
• Apply standard tags in stored content (posts, tips, profiles) where language is relevant.
• Document supported locales and fallback strategy.