fix(ci): regenerate lockfile with npm 10 to match Cloudflare Pages

Cloudflare's build runs `npm clean-install --progress=false` with
npm 10.9.2 / Node 22.16.0. Local dev had npm 11.6.2 / Node 24, and
the lockfile npm 11 produces lays out some transitive entries
(emnapi, esbuild peer ranges) in a shape npm 10's strict mode
rejects with `Missing: <pkg> from lock file`.

Reproduced locally and fixed:
  $ rm -rf node_modules
  $ npx -y -p npm@10.9.2 npm install
  # 91 insertions, 27 deletions in package-lock.json
  $ rm -rf node_modules
  $ npx -y -p npm@10.9.2 npm clean-install --progress=false
  added 1029 packages, exit 0

Also adds frontend/.nvmrc=22 so future contributors and any CI that
respects nvmrc default to a Node version with bundled npm 10.x. This
is the same Node version Cloudflare Pages picks from environment.

No package.json version changes. Frontend tests + typecheck unchanged
(18/18 pass, typecheck clean).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Jose-Gael-Cruz-Lopez

frontend/.nvmrc

@@ -0,0 +1 @@
+22