Save consent without reloading the page

consent.js posts the consent form in the background, the server answers
204 with the cookie, and the script swaps in the embeds and the legal line
from a fresh copy of the page. Embed hosts are in frame-src from the start,
the content address still only after consent. Without JavaScript the form
keeps working with a reload.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

templates/page.html.twig

@@ -70,6 +70,7 @@
     {% if needsMotion|default(false) %}<script type="module" src="/assets/motion.js?v={{ kant_version() }}"></script>{% endif %}
     {% if needsScrolled|default(false) %}<script type="module" src="/assets/scrolled.js?v={{ kant_version() }}"></script>{% endif %}
     {% if needsZoom|default(false) or needsDocument|default(false) %}<script src="/assets/lightbox.js?v={{ kant_version() }}" defer></script>{% endif %}
+    {% if needsConsent|default(false) and not editing|default(false) %}<script src="/assets/consent.js?v={{ kant_version() }}" defer></script>{% endif %}
     {% if not editing|default(false) %}{% for src in pluginScripts|default([]) %}<script src="{{ src }}" defer></script>{% endfor %}{% endif %}
     {# Own scripts of this page, as a file. Never rendered in the editor preview: the preview must
        show the layout, not run code that could change the page under the editor's hands. #}