task: #3623204 Fix Stylelint failures in the GitLab CI pipeline.

stylelint --fix clears 186 of the 193 problems. The remaining five are rgb(r g b / a) values: the rule reports them as fixable but will not downgrade modern notation to the legacy comma form, and converting them by hand trips the paired color-function-alias-notation rule, which wants legacy commas with the rgb alias rather than rgba. A second --fix settles it.

The reformat expands the reduced-motion rule across several lines, which breaks a test asserting on its literal text, so flash.test.js is made whitespace-insensitive in the same commit rather than re-encoding a layout that the next --fix would change again.

Declaration counts per file are unchanged and the only value changes are notation normalisations, so the cascade is unaffected.

Closes #3623204