[i18n] Language Switcher, Middleware & Locale Management

[fbenmadani]

Implement the core internationalization (i18n) foundation required before RTL support.

This issue is a dependency for: SF-13 (RTL Support).

Scope:

• Backend locale handling
• Middleware for language detection
• Frontend language switcher UI

Tasks:

1. Middleware (Backend)

• Create SetLocale middleware
• Detect locale from:
  • User preference (if authenticated)
  • Session / cookie
  • Fallback to default (config/app.php)
• Apply App::setLocale()

2. Language Persistence

• Store selected language in session or cookie
• (Optional) Persist in user profile

3. Frontend Language Switcher

• Add language selector component (dropdown)
• Allow switching between at least: en, ar, fa
• Trigger backend route to update locale

4. Routes & Controller

• Create route: /locale/{lang}
• Validate allowed locales
• Store selection and redirect back

5. Config

• Define supported locales in config (e.g. config/locales.php)
• Example: ['en', 'ar', 'fa']

6. Blade / Frontend Integration

• Ensure all UI uses translation files (no hardcoded strings)
• Prepare layout for dynamic dir() later (RTL dependency)

Outcome:

• Users can switch language dynamically
• Locale is persisted across sessions
• Application is ready for RTL implementation (SF-13)

Notes:

• Keep middleware lightweight (runs on every request)
• Avoid coupling locale logic with tenancy unless required
• Prepare for future translation file expansion

[linear]

SF-14