* fix: remove probability sum validation and add batch save with total EV
- Remove the requirement that manual probabilities sum to 1.0, allowing
partial distributions (e.g. when a participant has <100% chance of top 8)
- Replace per-row save buttons with a single "Save All" button that submits
all participants at once
- Add a Total EV row at the bottom of the table summing all participant EVs
- Update action to batch process all participants from a single form submission
https://claude.ai/code/session_01WHRynBCcugSK7HHEmN6Yuy
* fix: validate participantIds server-side instead of trusting form input
Fetch participants from the DB in the action using the season ID from
the URL params, eliminating the untrusted participantIds hidden field.
Remove the now-unused hidden input from the frontend form.
https://claude.ai/code/session_01WHRynBCcugSK7HHEmN6Yuy
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Co-authored-by: Claude <noreply@anthropic.com>