ci(node): read the node version from .nvmrc and bump setup-node to v4

[JamieRuderman]

Follow-up to #1183. That PR pinned node-version: 22 in each workflow to clear the require(esm) floor electron-builder 26.15 introduced, which left the Node version specified in two places. .nvmrc already says v22.14.0, so the workflows now read it instead:

      - uses: actions/setup-node@v4
        with:
          node-version-file: .nvmrc

Applied to all four workflows (typecheck, build-electron, build-android, build-ios). CI now tracks .nvmrc exactly — 22.14.0 rather than "latest 22.x" — so a future bump there carries CI with it, and CI matches what developers get from nvm use.

Two places can't read the file and stay manual:

• .circleci/config.yml needs a literal image tag (cimg/node:22.23.2)
• Amplify's Node comes from the console's Live package updates setting (currently 22)

Both are above the floor. Anything that moves .nvmrc below 20.19 / 22.12 would break the electron workspace's postinstall, so these want a glance if that version ever drops.

setup-node v4

Second commit bumps actions/setup-node@v3 → @v4 in build-electron, build-android and build-ios (typecheck was already on v4). v3 runs on the deprecated node16 action runtime, which GitHub warns about in current run logs. node-version-file behaves the same on both, so this is a runtime bump rather than a behavior change.

actions/checkout@v3 is still in those three workflows and has the same deprecation, but it's left alone here — worth its own pass.

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