fix(frontend): meet WCAG AA contrast on the config-block link text
The Storybook accessibility test flagged the share-link <code> block: with no
explicit color it inherited a muted grey that renders as #888888 on the
#f8f8f8 tertiary-fill background in CI's Chromium — a 3.33:1 contrast, below
the 4.5:1 AA threshold. Set the text to the theme's primary text token so the
colour is explicit and high-contrast in both light and dark themes instead of
depending on an inherited value that varies by browser.
MHSanaei