LeagueRun beta update: divisions, fields, and cleaner registrations

A big batch of commissioner tools just landed in the beta.

Run your own league structure

• Add, rename, and retire divisions yourself, no support request needed
• Manage your practice and game fields the same way
• Game fields and practice fields are now tracked separately, so a field can't get double-booked across the two schedules
• Deleting a division, team, or field now warns you about everything attached to it instead of silently cascading

Registration cleanup tools

• Move registrants between divisions in bulk
• Wipe and restart a season's registrations when an import goes sideways
• Smarter duplicate detection catches likely duplicate registrants, not just exact matches within one import
• Imports now support a parent-requested coach field for team placement

Fixes

• Creating practice slots from the empty state works again
• Roster handoff codes to SquadRotate are now locked to the coach they were issued to, with tighter expiry