use zod for register verification

src/routes/register/Register.svelte

@@ -4,6 +4,7 @@
 	import { createEventDispatcher, onMount } from 'svelte';
 	import { env } from '$env/dynamic/public';
 	import { rulesShort } from '$lib/rules';
+	import { RegisterSchema } from './schema';
 
 	const dispatch = createEventDispatcher();
 
@@ -40,21 +41,18 @@
 	async function sendRegister() {
 		// eslint-disable-next-line no-async-promise-executor
 		registerRequest = new Promise<void>(async (resolve, reject) => {
-			if (
-				(birthdayInput.valueAsDate || new Date()) >
-				new Date(Date.now() - 1000 * 60 * 60 * 24 * 365 * 6)
-			) {
-				reject(
-					Error(
-						'Bitte gib Deinen vollständigen Geburtstag und die korrekte Jahreszahl an. Du musst mindestens 6 Jahre alt sein.\n'
-					)
-				);
+			const parseResult = RegisterSchema.safeParse(
+				Object.fromEntries(new FormData(document.forms[0]))
+			);
+
+			if (!parseResult.success) {
+				reject(Error(parseResult.error.issues.map((i) => i.message).join('\n\n')));
 				return;
 			}
 
 			const response = await fetch(`${env.PUBLIC_BASE_PATH}/register`, {
 				method: 'POST',
-				body: new FormData(document.forms[0])
+				body: JSON.stringify(Object.fromEntries(new FormData(document.forms[0])))
 			});
 			if (response.ok) {
 				dispatch('submit', {
@@ -80,7 +78,7 @@
 	let rulesAccepted = false;
 	let rulesModal: HTMLDialogElement;
 	let rulesModalSecondsOpened = 0;
-	let rulesModalTimer: number | null = null;
+	let rulesModalTimer: number | NodeJS.Timeout | undefined = undefined;
 
 	let inputsInvalidMessage: string | null = 'Bitte fülle alle erforderlichen Felder aus';
 	let registerRequest: Promise<void> | null = null;
@@ -248,7 +246,7 @@
 	class="modal"
 	on:close={() => {
 		clearInterval(rulesModalTimer);
-		rulesModalTimer = null;
+		rulesModalTimer = undefined;
 	}}
 	bind:this={rulesModal}
 >