Update backend URLs to use environment variables

Replaced hardcoded backend URLs with environment variables in contact, apply, and verify_email components. Added .env.development and .env.production files to define the base URLs for different environments. This improves flexibility and allows easier configuration changes.

src/components/verify_email/verify_mail.tsx

@@ -42,7 +42,7 @@ const VerifyMail: FC = () => {
             eMail: email
         }
         console.log(verificationData);
-        fetch('https://forms-backend.alttd.com/api/verify_email/form', {
+        fetch(`${process.env.REACT_APP_BACKEND_BASE_URL}/api/verify_email/form`, {
             method: 'POST',
             headers: {
                 'Content-Type': 'application/json',