Fix ScaleManager scroll bounds after page scrolling

[SaveEditors]

Fixes #7203.

ScaleManager stores canvas bounds in page coordinates, but getParentBounds() compared them with viewport-relative coordinates from getBoundingClientRect(). After the page scrolled, an unchanged canvas could be treated as having moved and trigger a refresh on every resize interval.

The bounds check now converts the current canvas rectangle to page coordinates using the same calculation as updateBounds() before comparing it with the cached bounds.

Regression tests cover horizontal and vertical scrolling, document client borders, parent resizing, actual canvas movement, and fixed-position canvas settling.

Validated on Windows with:

• npm test -- tests/scale/ScaleManager.test.js tests/scale/const
• npm run build
• node --check src/scale/ScaleManager.js
• node --check tests/scale/ScaleManager.test.js
• git diff --check