CSS and template overrides for WCAG 2.1 AA compliance.
V3 (#547): Footer text contrast
- Darken footer text to #767676 (4.54:1 on white)
- Was light gray, failed 4.5:1 minimum
V4 (#548): Green inline links contrast
- Darken link color to #507020 (4.5:1 on white)
- Add underline for non-color differentiation (SC 1.4.1)
- Was #609926, failed 4.5:1
V5 (#549): Header/banner landmark
- Add <header role="banner"> wrapper template
- Screen readers now find the banner landmark
- Was missing entirely (landmarks.banner: 0)
Note: V6 (#550, h4→h1 on login) already fixed in PR #559.
Closes#547, #548, #549
