feat: delete legacy marketing static templates and their URL routes

Remove the 14 template files that were served locally when
ENABLE_MKTG_SITE=False. These pages (about, blog, contact, donate, faq,
help, honor, jobs, media-kit, news, press, privacy, tos, sitemap.xml)
should now only live on the external marketing site configured via
MKTG_URLS.

Also remove the stanford-style theme overrides for about.html and
tos.html, the hardcoded URL patterns for the deleted templates, the
honor.html iframing special case from the render view, and the tests
that exercised these now-deleted routes.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>