[WCAG] Contrast issues across the application

1) What is your original issue/pain point you want to solve?

https://webaim.org/articles/contrast/

2) Which are one or two concrete situations where this problem hurts the most?

Overview listings, breadcrumbs, and icons.

There are currently a lot of cases where the contrast on text/icons against the background is too low.

3) Why is it not solvable with the Zammad standard?

Because the css is incorrect at its core

4) What is your expectation/what do you want to achieve?

Updating some of the color variables, and setting a few small css tweaks should help.

:root {
    // Replacements
    --text-link: #2F6FA7;
    --menu-icon: #BDBDBD;
    --button-primary-background: #257BB1;
    --text-muted: #6F7476;
    --interactive-muted: #686C6E;
    --button-action-color: #686C6E;
    --text-nav: #2F6FA7;
    --menu-icon-secondary: #9495A4;
    --ok-color: #9E6C00;
    --supergood-color: #2A834F;
    --danger-color: #e01f1f;
    --header-secondary: #6B6B6B;
    --border-alt: #6B6B6B;
}
.item--low-priority a {
    font-style: italic;
    color: var(--text-link);
}
#global-search {
    border: 1px solid;
}
.tabsSidebar-tab .icon {
    fill: var(--interactive-muted-alt-selected);
}
.tabsSidebar-tab.active .icon {
    fill: var(--ok-color);
}
.item--high-priority a {
    color: --danger-color;
}
div.box .form-control {
    border-color: var(--border-alt);
}

The accessibility will be improved with the new desktop-view.