[CLOV-1600][BpkScrollableCalendar] Bump react-window to v2

[Vincent Liu (xiaogliu)]

Summary

CLOV-1600. Replaces the previous draft migration in #4477 with a version rebased onto the current main repository structure.

Migrates the only react-window consumer, BpkScrollableCalendarGridList, from v1 to v2:

• List replaces VariableSizeList; rendering now uses rowComponent + rowProps
• rowCount / rowHeight replace v1 itemCount / itemSize
• useListRef + scrollToRow replaces the old initial pixel offset path
• react-virtualized-auto-sizer is removed because v2 has built-in sizing
• @types/react-window is removed because v2 ships its own types
• ResizeObserver is mocked in the affected jsdom tests
• Scrollable calendar snapshots are regenerated for the v2 DOM structure
• Adds a changelog entry and Dependabot major-version ignores for react-window / @types/react-window

Validation

• npx eslint packages/backpack-web/src/bpk-component-scrollable-calendar/src/BpkScrollableCalendarGridList.tsx packages/backpack-web/src/bpk-component-scrollable-calendar/src/BpkScrollableCalendarGridList-test.tsx packages/backpack-web/src/bpk-component-scrollable-calendar/src/BpkScrollableCalendar-test.tsx packages/backpack-web/src/bpk-component-scrollable-calendar/src/accessibility-test.tsx --ext .ts,.tsx
• TZ=Etc/UTC npx jest packages/backpack-web/src/bpk-component-scrollable-calendar/src/BpkScrollableCalendarGridList-test.tsx packages/backpack-web/src/bpk-component-scrollable-calendar/src/BpkScrollableCalendar-test.tsx packages/backpack-web/src/bpk-component-scrollable-calendar/src/accessibility-test.tsx
• npm run check-bpk-dependencies
• npm run check-react-versions
• npm run lint exits 0; existing repo warnings still print
• npm run jest passes: 390 suites passed, 1 skipped; 2666 tests passed, 3 skipped; 825 snapshots passed
• npm run typecheck currently fails on existing story declaration issues for bpk-component-price / bpk-theming; no scrollable-calendar or react-window errors were reported before those failures
• Storybook manual validation still needed for initial scroll, variable row heights, RTL, font scaling, resize, date selection, and side-by-side visual comparison

Notes

This supersedes #4477. #3997 is already closed.

[Vincent Liu (xiaogliu)]

There are no security vulnerabilities in @react-window and @types/react-window version 1.x, and their current features meet our requirements. However, version 2.x comes with API changes and will alter the behavior of bpk-component-scrollable-calendar. Taking the development effort, risks and practical benefits into consideration, I believe there is no need to upgrade @react-window and @types/react-window to version 2.0 for now so close this PR