Add minimum width to buttons

This ensures they aren't too small, even if the text label is short.

app/styles/input.css

@@ -176,6 +176,7 @@ input[type=submit],
 input::file-selector-button,
 button,
 select {
+    min-width: 8em;
     border: none;
     color: black;
     font-weight: bold;