Create and add C4 model documentation

[Malaguth]

docs: Add and update the drawio C4 model

• The c4 model is a work in progress (WIP)

docs: Split functional and technical info, also add c4 model page

• Create a folder for functional docs and update the previous links
• Create a folder for technical docs, add a c4 model page, and add links to the readme

[ViniciusLAAraujo]

We have images in dark and light modes. It would be good to define a pattern and follow it.

I've changed all of them to black background to be the same