Various display issues on broadcast page

[rmarquis]

Here are a few issues I see while using the broadcast section, in various page width depending on how the website is set up on the screen (full, half, and small column width):

Full width

• The "Round" section is not properly themed.
• There is missing space between the round section and chat section
• The move section doesn't use all the available space on the right
• The evaluation gauges on the small boards is not prettified, it still use the vanilla lichess gradient

Medium width

• Pretty much the same as above.
• The "Round" section is not aligned with the move section, and also not using the available space on its right.

Small width

Same issues as above, with in addition:

• Name, rating, clock of top-board player isn't visible
• The menu bar is transparent and displayed above the board (it's similar to The transparent header bar reappears and overlaps content when scrolling up #208 but not exactly the same, as the problem is always present, not only when scrolling up)
• Missing space on the right side of the board, partially preventging the clock to be displayed correctly (I am not able to make it display correctly even when resizing the window)
• (in green) Do note that unlike the lichess theme, prettier lichess is able to display both the moves and the evaluation sequence moves. Only the latter is visible with the vanilla lichess theme. There is however too much unused space, pushng the rest of the page further down.