css: adjust lightmode input bg colors for improved visibility

css: adjust lightmode input bg colors for improved visibility

In the light theme, form controls using browser defaults often
lack contrast with the page background, making them less easy to
identify as interactive fields. Give inputs and textareas a
distinct background so they are visually identifiable from
surrounding content without being distracting.

#cfc is salient enough to stand out across low-to-high brightness
settings consistently. It is not intense. It fits naturally
within a light mode palette and does not require inverting the
text color to maintain readability (no extra CSS).

Signed-off-by: Rito Rhymes <rito@ritovision.com>