Add Italian (QWERTY-IT) keyboard layout

[AshBuk]

Add the Italian QWERTY layout (ISO 105-key, used in Italy).

File: gui/src/js/layouts/it-qwerty.js
Reference: fr-azerty.js — closest analogue (ISO with accents). Keep field order and code style consistent.

After creating the file, register it in layouts.js and add the <script> tag in gui/index.html. Apache-2.0 license header at the top.

Checklist:

• Renders correctly in make dev, finger highlighting works for all keys
• make lint, make test, wails build pass
• Verified by a native Italian typist (mention in PR)

Setup: docs/CONTRIBUTING.md. Difficulty: easy.