[DOCS] New tutorial sections

[AlexandreSajus]

Issue Description

Currently, the "Visuals" section has the tutorials "Long Running Callbacks" "Real-Time Data Visualization with Multithreading" and "Managing Multiple Users". The "Fundamentals" section has the tutorials "LLM Chatbot" and "RAG Chatbot".

These tutorials seem out of place and will, therefore, be hard to find.

Screenshots or Examples (if applicable)

Proposed Solution (optional)

I suggest moving them into new sections, such as "Backend" and "AI," respectively.

Code of Conduct

• [X] I have checked the existing issues.
• [X] I am willing to work on this issue (optional)