[feat] Enhance NewForm and useNewForm with event type utilities, date validation, and backend integration

[Aloento]

Summary of the Pull Request

This pull request introduces several improvements and new features to the NewForm component and the useNewForm hook, focusing on enhancing functionality, user experience, and maintainability. The changes include the following:

Key Changes:

1. Loading State for Submission

   • Added a loading state to the NewForm submission button to improve user feedback during event submission.

2. Backend Integration for Event Submission

   • Updated useNewForm to handle event submissions with integration to the backend API.

3. Event Type and Impact Utility Functions

   • Implemented utility functions to retrieve event types based on impact values and vice versa, centralizing and simplifying event type logic for better code maintainability.

4. Refactor Event Type Determination

   • Leveraged the GetEventType utility function for cleaner and more consistent event type determination.

5. Date Formatting and Localization

   • Updated NewForm to use dayjs for datetime formatting.
   • Added clear labels for CET time zone in displayed date fields.

6. Enhanced Date Validation Logic

   • Improved date validation logic in useNewForm, ensuring that end dates reset appropriately when the event type changes.

[anton-sidelnikov]

Looks good