Refactor MyPacks and PackUploader components to utilize APIClient for data fetching and uploading

Commit notes

- Replaced direct fetch calls with APIClient methods in MyPacks for loading user sample packs and deleting packs, improving code maintainability. - Updated PackUploader to use APIClient for creating sample packs and uploading samples, enhancing consistency across API interactions. - Cleaned up unused token retrieval logic and streamlined state management in both components for better performance and readability. - Enhanced error handling and user feedback during upload processes, ensuring a smoother user experience.