fix(a11y): unreadable image captcha with dark themes (#7390)
- When the user has a dark theme selected, image captchas are sometimes unreadable.
- Make sure the image captcha always has a white background color.
Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/7390
Reviewed-by: 0ko <0ko@noreply.codeberg.org>
Reviewed-by: Beowulf <beowulf@beocode.eu>
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Andreas Shimokawa <shimokawa@fsfe.org>
Co-committed-by: Andreas Shimokawa <shimokawa@fsfe.org>
authored by