chore: bump vitest 3.2.7 -> 4.1.10 (Dependabot #5)

Vitest 4 peers on vite ^6||^7||^8 -- Mill's frontend is already on
vite 8.2.1, so this is a clean, isolated bump with no vite cascade
(the hypothetical vite-5 scenario the goal brief flagged doesn't
apply here). vite.config.ts's `test` block is a plain `exclude` array
(no `workspace` config), so the workspace->projects rename in vitest
4 doesn't touch this repo either.

No source changes needed -- package.json/package-lock.json only.

Full local suite green: 231/231 vitest tests (29 files -- the jump
from 227/28 reflects goal 0037's seedLifecycle.test.ts merging to
main concurrently, not a vitest 4 behavior change, confirmed by
diffing the file list), eslint (0 errors, 4 pre-existing warnings),
tsc, boundaries, frontend build, go vet, go build (desktop+server),
file-loc-limit, root-file-naming.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FYwojT8GdUbYSoggbvEFft

Author: alicoding