Adds a Clone Season button on the admin sports season detail page. The
clone form pre-fills all settings with the source season's data, bumping
the year by one and shifting all dates accordingly. On submit, the new
season is created in a single transaction that copies participants,
scoring events (with dates shifted), futures odds/Elo rating stubs
(zeroed-out probabilities so the simulator can re-run), and QP config
for qualifying_points seasons.
Fixes#282
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
