feat: make loading screen background dark

[kof]

Description

A better looking loading screen

Steps for reproduction

1. click button
2. expect xyz

Code Review

• hi @kof, I need you to do
  • conceptual review (architecture, feature-correctness)
  • detailed review (read every line)
  • test it on preview

Before requesting a review

• made a self-review
• added inline comments where things may be not obvious (the "why", not "what")

Before merging

• tested locally and on preview environment (preview dev login: 0000)
• updated test cases document
• added tests
• if any new env variables are added, added them to .env file

[johnsicili]

Is there a way to combat this white screen? Even if its just setting the default color to the same of the loader, that will look better. White screen with nothing seems like there is some issue.

loader.mp4

[kof]

Good idea actually

[kof]

done, check it out

[johnsicili]

Looks better. I don't know if its related to this PR, but when I access a Project via a share link, the loading screen doesn't go away

[kof]

reverted back the fix I was trying to make in parallel to the background change, which is about waiting for selected instance, before closing the overlay, currently its still having some movement after its loaded I wanted to avoid for a better effect, but seems too hard

@johnsicili good catch with this one