Sigma Gestionnaire de Média 1.3.1

Fixed
- Session expiration handling across all API calls — expired nonces now trigger an automatic page reload instead of showing a generic error
- Document Library frontend now properly detects and handles 401/403 authentication errors when fetching items or verifying captcha
- Document Library Admin folder fetching, item loading, folder creation, and item reordering now handle session expiration gracefully
- Media Library Folders (create, rename, delete, move) now detect session expiration and auto-refresh instead of showing unhelpful error messages
- Duplicate page refresh prevented by throttling auto-reload to once per 5 seconds using sessionStorage

### Added

- Admin API notification system with countdown timers
- Multi-AI Provider Support: Now supports Free Credits, Gemini, OpenAI, and Claude AI providers
- Tab-based provider selection in AI Settings with individual API key configuration
- Real API key validation for all providers (Free Credits, Gemini, OpenAI GPT-4o, Claude 4 Sonnet)
- Provider-specific API integration for text generation
- Dynamic provider selection that applies to all AI text generation features
- Dashboard feed widget with styled RSS posts, banner image, badges, and footer links on the WordPress dashboard

### Improved

- AI text generation now uses the selected provider from settings instead of only Gemini
- Provider-agnostic error messages throughout the application
- API key availability checks now work with any configured provider