feat: remove ENABLE_MKTG_SITE from LMS branding views

index() (served at /) now unconditionally checks MKTG_URLS['ROOT'] and
redirects when it differs from LMS_ROOT_URL, matching the previous
ENABLE_MKTG_SITE=True behaviour. The catalog MFE redirect
(ENABLE_CATALOG_MICROFRONTEND) still fires first and is unaffected.
Also fixes a pre-existing bug where log.error() in the NoReverseMatch
handler was passed multiple f-strings as positional args, causing a
TypeError when that branch was reached.

courses() (served at /courses) now resolves in priority order:
1. Redirect to the catalog MFE if ENABLE_CATALOG_MICROFRONTEND is set
2. Permanent redirect to marketing_link('COURSES') from MKTG_URLS
3. Render the local course list via courseware.views.views.courses()

The old ENABLE_MKTG_SITE gate and COURSES_ARE_BROWSABLE guard are
removed. The local course list fallback (case 3) preserves behaviour
for operators who have neither the catalog MFE nor MKTG_URLS['COURSES']
configured.

The stanford-style theme footer is updated to use marketing_link()
instead of reverse() for the 'about' and 'tos' URL routes, which are
removed in a later commit.

Tests drop their @override_settings(ENABLE_MKTG_SITE=True) decorators;
the test names and assertions are otherwise unchanged.

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