Replace the fragile approach of computing rowHeightPx by dividing
Column height by weeks count with direct measurement via onSizeChanged
on the first DayCell row. Add estimated row height fallback based on
screen width and cell aspect ratio so the pager can be constrained
before the first measurement completes. Remove lockedRowHeightPx,
expandedWeeksCount, and calendarHeightPx state variables that are no
longer needed.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>