Refactor notification handling in AuthProvider and queries to utilize TanStack Query mutations

Commit notes

- Removed direct notification calls from AuthProvider for login and registration, centralizing notification handling within the respective mutation hooks. - Updated useLoginMutation and useRegisterMutation to show success and error notifications upon mutation completion, enhancing user feedback. - Refactored other mutation hooks to include success and error notifications, ensuring consistent user experience across the application. - Cleaned up AuthPage to reflect changes in notification handling, improving code maintainability.