Support weighed quantities in mobile POS sales

[sridharkalaibala]

Weighed products configured with a selling unit can be sold from a capable mobile client using up to three decimal places. Bootstrap requires an explicit fixed-quantity opt-in; older clients and items with unsupported modifiers/discounts remain blocked. The issuing catalogue grant controls permitted precision, money uses integer minor-unit rounding, and receipt history retains the validated unit.

Retries reuse the existing mobile sale/stock identity. The phone asks for quantity before adding a weighed item and keeps the current void permission for reductions.

Validation: 23 real mobile/POS integration cases; 11,585 API tests passed (13 skipped); 3,639 desktop tests passed (5 skipped); API docs and attribution checks pass. Integration covers legacy-client exclusion, invalid/forged precision, stored units, and one stock effect after replay. Paired mobile checks: 73 unit tests and 34 browser tests, including HID quantity entry. Android release builds and Windows payload hashes verified. Attached weighing hardware is not claimed; this is entered quantity in the configured unit.

Open-price items are explicitly blocked until mobile price entry is supported, preventing a stored/default price from bypassing the required prompt. The regression is covered by the real integration suite. The latest upstream kitchen-label change is included; its 20 targeted tests pass.

[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.