Make restock supplier search safe and align the dialog

[sridharkalaibala]

The restock supplier selector is searchable, and core navigation shortcuts now ignore open dialogs, open searchable dropdowns and focused editors. Typing supplier names cannot navigate away from the restock basket. The dialog has aligned quantity controls, a touch-sized supplier picker, proper spacing below it and equal-width finish actions.

Validation: 17 local shortcut/restock tests passed; frontend build, formatting, diff and attribution checks passed. On the isolated demo, typed supplier and g using keyboard events and verified the page remained on Low Stock; Enter selected General Supplier. Matching/no-match search and supplier/item/quantity purchase handoff were also verified. Production unchanged.

[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.