(SP: 1) Create informational pop-up window

## Description
Implement the informational pop-up window according to the mockup.

## Design


## Acceptance Criteria
- [ ] If a user clicks on the close button the pop-up window must disappear.
- [ ] The pop-up window must not disappear if the user clicks on the area of the sign-up form

Start by reviewing the linked mockup and locating the existing sign-up form area in the frontend. Implement the informational pop-up so the close button dismisses it while clicks inside the sign-up form do not, then verify both acceptance criteria manually.

Written by the indexing model from the issue text.