Improve Authentication Email Deliverability

Description: I noticed that authentication code emails sent by the platform often go into the spam folder of email accounts. The email template currently includes links, which may contribute to the issue of emails being flagged as spam. I propose modifying the email templates to remove links from the footer (e.g., the logo link and the 'Powered by Sleekplan' link). Problem: Emails containing authentication codes are ending up in users' spam folders, reducing the usability of the product and increasing confusion for users who might think the emails weren't sent. Benefit: Removing links from the email templates could improve email deliverability and reduce the chance of messages being flagged as spam. This change would ensure a better onboarding experience and enhance user satisfaction by minimizing frustrations related to email authentication issues.