build: upgrade all npm dependencies (#180)

* build: upgrade all npm dependencies

Major bumps:
- vitest 3.2.4 → 4.1.0
- jsdom 26.1.0 → 29.0.0
- @cloudflare/workers-types 4.20260310.1 → 4.20260317.1

All 129 web tests pass with the new versions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* build: require node >= 24 for web dependencies

vitest 4, jsdom 29, and vite 8 (transitive) all require modern Node.
Add explicit engines field so installs fail fast on unsupported versions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: danielewood