Keep KOT computers awake and protect saved hardware settings

[sridharkalaibala]

KOT printing now holds the system sleep blocker only while kitchen polling is active. Pausing printing or quitting releases it; screen lock and display sleep remain available. Hardware Manager explains this without moving the cursor or producing paper.

Hardware preferences and KOT configuration flush a temporary JSON file before replacing existing settings, and user saves report write failures. Fix the missing Electron import that hid saved kitchen printer assignments. The uninstaller explicitly explains that Keep my data retains printer selections and hardware settings for test reinstalls; deliberate Delete everything remains respected.

Validation: 70 focused power, settings, installer and Windows printer tests passed. Full desktop run: 3,473 passed, four skipped, three test-harness failures (Windows line endings and an incomplete console mock). Fixed those harnesses and reran both affected files: all 27 tests passed. Document printing persistence tests also passed. Attribution check passed.

No physical idle/reconnect or destructive uninstall was performed on the customer's computer. These changes cannot guarantee USB extender connectivity or recover already deleted settings. Ordinary auto-update and keep-data uninstall already retain the user data directory; the historical reason for this user's missing settings is not established.

[github-actions]

Merged to develop. Anyone can test this - you do not need write access.

Try it at https://develop.posnic.io, or run it yourself:

git fetch origin develop && git checkout develop
npm install && npm --prefix api install
npm run dev   # then http://localhost:3000

When you have tested it, say what you did and what happened, and set
QA passed or QA failed. If you cannot set labels, just comment -
a maintainer will.

Reporting that something is broken is as useful as fixing it. It is
better found here than by a shopkeeper.