- Introduced `PlayoffRound` model with cost inputs for games, umpires, balls, and fields.
- Added UI to manage multiple playoff rounds, each with configurable fields.
- Extended cost computations to include playoff-specific totals for umpires, balls, and fields.
- Updated import/export logic to handle a new save file version (v2) including playoff data.
- Implemented `localStorage` auto-save/load for persistence across sessions.
