Fix various small code issues with onboarding

[danieladugyan]

• The initial page response has "Program" set to "Datateknik", but upon loading it is blank instead (inspect response in developer tools).
• Instead of using required=true for form fields, define required in the zod schema.
• Remove the form id
• Consider moving the onMount redirection to server-side for additional performance.

• Remove/explain odd usage of Prisma.allSettled. Maybe it should be like this instead?

  // src/routes/(app)/onboarding/+page.server.ts
  export const load: PageServerLoad = async ({ locals }) => {
  const { prisma } = locals;
  
  let member: Member | null;
  try {
  member = await prisma.member.findUnique({
    where: {
      studentId: locals.user?.studentId,
    },
  });
  } catch (e) {
  redirect(302, "/"); // why this though?
  }
  
  if (!member) {
  throw error(404, m.onboarding_errors_memberNotFound());
  }
  return {
  form: await superValidate(member, memberSchema),
  member,
  };
  };