Add reusable form button component with props and useSubmitButton hoo…

[MohammedAbi]

…k. Update index.css for styling

What does this PR do?

• Adds a reusable SubmitButton with async loading and success states, plus related styling updates

• Description of Task to be completed?

• Implement a button component that handles async submit actions with loading and success feedback.
• Update styles to support the new button UI and animations.

How should this be manually tested?

• Integrate the SubmitButton in a form.
• Click the button to trigger submit.
• Verify the loading animation appears during submission.
• Confirm the success icon shows after successful submission and button disables temporarily.

Any background context you want to provide?

• This component is designed for reuse across forms needing async submission with user feedback.

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