Fix horizontal overflow: overflow-x-hidden on body and app, remove shrink-0 from 42ch spans

The 42ch fixed-width spans with shrink-0 prevented flex from shrinking
them when the container was narrower, causing horizontal scrolling.
Also added overflow-x: hidden on body and #app as a safety net.

src/popup/views/helpers.js

@@ -76,7 +76,7 @@ function balanceLine(symbol, amount, price) {
     const usd = price ? formatUsd(amount * price) : "";
     return (
         `<div class="flex text-xs">` +
-        `<span class="flex justify-between shrink-0" style="width:42ch">` +
+        `<span class="flex justify-between" style="width:42ch">` +
         `<span>${symbol}</span>` +
         `<span>${qty}</span>` +
         `</span>` +