Screen readers navigate by landmark, but only /config had a <main>; everywhere else the page content sat outside any landmark, and keyboard users tabbed through about 20 navbar links before reaching it. base.html now wraps the content block in <main id="main-content">, labels the navbar "Main", and opens every page with a "Skip to content" link that appears on focus and moves focus into the main region. The login card is the login page's main.
/config had its own <main>, which would have nested inside the new one, so its panel column is a plain div. Its sidebar group names (Core, Database, Admin Tools) were h6 headings ahead of the page's h5 sections, which broke the heading order and left three unlabeled navigation landmarks; they are now paragraphs that label their nav.