feat: nginx sec headers

[Lennart01]

Description

Changelog

Checklist

• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] The light- and dark-theme are both supported and tested
• [ ] The design was implemented and is responsive for all devices and screen sizes
• [ ] The application was tested in the most commonly used browsers (e.g. Chrome, Firefox, Safari)

(Optional) Visual Changes