Have blocking messages and dialogs vertically centered #420
Description
In https://opencor.ws/app, blocking messages (e.g., the Initialising OpenCOR... message we get when loading OpenCOR) and dialogs (e.g., the Open Remote... dialog) are vertically centered against the viewport MINUS the menu bar:
This is exactly what we want, BUT... this is not good because the menu bar is still usable while we want all of OpenCOR to be disabled when showing a blocking message or a dialog. We can easily block all of OpenCOR but then blocking messages and dialogs are not vertically centered, as can be seen in https://opencor.ws/appdev:
The difference between https://opencor.ws/app (see https://github.com/opencor/webapp/tree/v0.20260215.0) and https://opencor.ws/appdev (see https://github.com/opencor/webapp/tree/22c63e6497e5b8be28a35b316186bf223e5e014a) is that all the blocking messages and dialogs are within a div element, so that they can be vertically centered, but as we can see this results in the menu bar remaining usable, which is not what we want.
Something that has been tried is to remove the div, track the height of the main menu (just to be on the safe side) and use CSS to translate-y the blocking messages and dialogs. This works in the sense that they are vertiaclly centered AND that the main menu is NOT usable, BUT... then if we move a dialog then it will eventually move to the bottom of the viewport and all we can do from there is to move it to the left or right. This is clearly not good, hence that approach was discarded and we are now back to what we have in https://opencor.ws/appdev.
Yet, aeshetically speaking, it doesn't look good to have those blocking messages and dialogs not vertically centered. So, it would be good if we could somehow fix this.
@akhuoa, any idea how this could be done?