{# mirrorwall/base.html — the shell every application's pages extend. Slots, not pages (spec §3): this template renders whatever product name, navigation and footer the application supplies, and contains no application vocabulary of its own. An application extends it, overrides `content`, and supplies `product_name`, `product_version` and `nav_items`. The theme bootstrap is inline and tiny on purpose (UI standards §9): it must run before first paint or a dark-mode reader sees a white flash, and an external file is a second request that can lose that race. #}