Add environment variable validation and parsing

Adds a validation schema for the application's environment variables using the Zod library. The parsed environment variables are then exported as constants that can be imported throughout the application, replacing the direct use of process.env.

components/ui/alerts/ErrorAlert.tsx

@@ -16,7 +16,7 @@ const ErrorAlert: FC<ErrorAlertProps> = ({ error, setError }) => {
 
       <div className="flex-none">
         <button
-          className="btn btn-ghost btn-sm"
+          className="btn-ghost btn-sm btn"
           type="button"
           onClick={() => {
             setError('');