Make it look good on mobile

[IanWold]

Currently on mobile it looks ... interesting. The fixed-position buttons in the corners overlap with the UI buttons, the center table becomes too big, and it's tough or impossible to send stars to other participants.

The following should be done for mobile:

• The "add" and "help" buttons can be hidden for now; these are just nice-to-haves.
• The top and bottom bars should be made to stretch across the whole screen width with nice padding.
• The point buttons in the bottom bar should be made to wrap if there are too many for the width. Ideally, at least 8 should be able to fit across - this depends on screen size, of course.
• The "toggle color mode" button should sit next to and to the right of the top bar, so the top bar would stretch across the width of the screen minus the area occupied by the toggle button.
• The center table should instead be a list group of the participants. The user should be the first participant listed. Each list item should contain the participant's name and star count on the left and the star button on the right. When a participant has selected a point value, the background of their list item should be primary. When points are revealed, participants should be grouped into different list groups by point selected, with the respective point value displayed either above or to the left of each grouping. Unpointing participants should be at the bottom.
• The "reveal/hide" button should be above the list group(s) of participants.
• The modals to enter name and title should be made to stretch across the whole screen width with nice padding.

Any of the above can be done in a PR; it's OK for there to be multiple PRs for this so long as each PR is a deployable state.

If you want to take a subset of these bullet points on as a "good first issue", I would be more than happy to create a separate issue for you for that bullet point!