Summary: Diagnos adds new chat support feature

Why It Matters: This makes it easier for customers to ask questions and get help.

What Changed:

• Added a "Scroll to Top" button.
• Added an "Open chat" button.
• Added a chat message: "Halo sobat Diagnos ada yang bisa kami bantu ?"
• Updated image links for promotions to use newer filenames and .webp format.
• Updated some article links and titles in the "Baca Artikel Diagnos" section.