Fix content in the production deployment landing page

[tomislavmamic]

Navbar

• [x] Hide links to not-used pages: Projekti, Moj doprinos, Rezultati.
• [x] Show links to working pages: Dokumentacija, Forum,
• [x] Show links to page sections: Najčešća pitanja
• [x] Update proposal button link: https://forum.zazelenimo.com/t/uputa-za-podnosenje-prijedloga/15
• [x] Change notification bar text to this: Primamo prijedloge projekata do 1. rujna 2024. [Pošalji prijedlog sada.](https://forum.zazelenimo.com/t/uputa-za-podnosenje-prijedloga/15)

Footer

• [x] Remove Twitter, telegram and discord icons
• [x] Link Facebook to: https://www.facebook.com/parkovisplit
• [x] Link Github to: https://github.com/muqa-org/demo
• [x] Documentation link to documentation pages
• [x] Forum: add link to forum