Add cashier-scoped mobile receipt search and offline status guidance

[sridharkalaibala]

Mobile users can now find their older mobile receipts after local history cleanup. The new authenticated endpoint returns 50 results per page with stable newest-first pagination and literal receipt/customer searches. Tenant, branch and cashier identity come from the authenticated session; another user's receipts are excluded.

The Mobile POS settings page explains direct Bluetooth versus Till printing and prevents misleading expectations about duplicate receipt delivery. The kitchen-screen save status now exists in the base markup and is reused by the hardware layout.

Validation: 20 mobile/POS integration tests passed without skips, including real browser sign-in, offline sale, sync and server receipt lookup. API Jest: 440 suites / 11,569 tests passed (13 existing skipped tests). Desktop full suite found one markup-contract failure; fixed and all 27 targeted shell/hardware/kitchen tests passed. Mobile: 60 unit tests, 32 browser tests, type checking, formatting and attribution passed. Android test APK assembled. API docs and README endpoint count regenerated. Physical printer tests and cloud delivery acknowledgments are not claimed.

[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.