Courses can now only be added via Golf Course API import, which
provides the full data model: per-tee slope/rating/gender/SI
(stroke_indices JSON) and front/back split ratings. Manual creation
required admins to enter SI by hand and didn't match the API model.
Changes:
- Remove GET/POST /admin/courses/new routes and new_course.html
- Remove _parse_hole_form helper (no longer needed)
- Edit course: par-only editing; stroke_index preserved from import,
not exposed or overwritten in the admin form
- courses.html: replace "+ New course" with "+ Import course" button
- course_search.html: remove "+ Manual" shortcut
- edit_course.html: remove SI column from hole grid
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
