Upgrade Flutter SDK to the latest stable version

### Describe your improvement idea or feature request

The project is currently using an older Flutter SDK version (3.29.2), which may lead to compatibility issues with newer dependencies, tooling, and platform updates.

I would like to propose upgrading the Flutter SDK to a more recent stable version(3.38.5) to ensure better performance, improved tooling support, and long-term maintainability of the project.

### How would you like to see it implemented?

1. Upgrade the project to the latest stable Flutter SDK
2. Update the Flutter version constraint and related configuration files
3. Resolve any breaking changes, deprecations, or analyzer warnings
4. Update dependencies only where required for compatibility
5. Verify the app builds and runs correctly across supported platforms
6. Ensure existing functionality remains unchanged
7. Update documentation (e.g., README) to reflect the new Flutter version
8. Update workflows with new flutter version

### Put here any screenshots or videos (optional)

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### How can we contact you (optional)

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### Would you like to work on this issue?

None

### By submitting this issue, I have confirmed that:

- [x] I have starred the repo ⭐ and watched 👀 it on GitHub and followed the contribution guidelines.

Commencez par localiser la contrainte de version de Flutter, les fichiers de configuration associés, les définitions de workflows et les références au README mentionnés dans l’issue. Mettez à niveau le SDK et traitez uniquement les changements de compatibilité requis par les résultats de analyzer et de build. Vérifiez les builds des plateformes prises en charge et les fonctionnalités existantes, puis confirmez que la documentation et les workflows indiquent la nouvelle version.

Rédigé par le modèle d'indexation à partir du texte de l'issue.