fix(react): honor prefers-reduced-motion in the shared stylesheet

[ra-co88]

What

The shared stylesheet now honors prefers-reduced-motion: reduce: transition and animation durations collapse to 0.01ms and smooth scrolling is disabled, per the standard accessibility pattern.

Why

Users who set the OS-level reduced-motion preference were still getting full transitions and smooth scroll — the stylesheet never consulted the media query.

What changed

One media block in packages/react/src/styles/globals.css. No API surface change.

Test plan

CSS-only change; verified by toggling the OS preference and observing the shared UI (e2e hook available if maintainers want it recorded — happy to add the one-liner).

[ra-co88]

Heads-up on the red E2E (cloud 13of16) check here: it's failing on main itself (e.g. the Version Packages runs), so it's pre-existing rather than from this PR. It's the cap-eviction scenario tripping over workerd resetting session Durable Objects mid-initialize when the test opens its burst of sessions — diagnosis and a proposed fix in #1895.