Enonic UI: Fix ProjectSelectionDialog sizing

[edloidas]

The current dialog implementation does not fully match the design:

• The spacing between the header and the list is incorrect. In the design, there is 47px from the title to the first list item.
• There is 80px from the last list item to the bottom edge of the dialog.
• On small screens, the dialog should take the full available width of its container (portal), minus 20px of padding. The width transition should be smooth, without jumps.
• The gap between list items matches the design, but in use it feels off. We need to preserve item “positions,” but the selection should jump instantly to the next item on hover. This requires removing item gaps and adjusting the active area, while keeping the visual distance between text elements unchanged.

I suggest applying padding to the content/list to preserve spacing — including in longer, scrollable lists.

Also, please check how the dialog is rendered when there are no projects yet and fix it if needed. (If a user has all the right to create project, project must have a button to invoke project creation dialog.)