Light theme: the hero slider's and the quickstart link's focus rings are 2.26:1 #961

On the light theme three controls draw their focus ring in --ember-bright (#fb923c), which is 2.26:1 on white, under the 3:1 a focus indicator needs (WCAG 2.2 SC 1.4.11), so a keyboard user can lose track of focus:

• the home page's hero slider dots (.hero-slider-dot:focus-visible) and arrows (.hero-slider-arrow:focus-visible);
• the "open the wizard" link on quickstart.html (.link-cta:focus-visible), whose text colour (rgb(250, 134, 46) on white, about 2.4:1) is also under the 4.5:1 body text needs.

Measured in Chrome with data-theme="light". The browser wizard had the same problem on its fields, sliders and section headers; #954 switched those to --ember-deep (#c2410c, 5.18:1 on white) under [data-theme="light"].

Acceptance criteria

• Under [data-theme="light"] the three focus rings have at least 3:1 against their background; --ember-deep gives 5.18:1 on white.
• The .link-cta text has at least 4.5:1 on the light theme.
• The dark theme keeps its current colours.