test(mobile): add unit tests for mobile QR scanner screen and hook

[TechBroAfrica]

closes #829

test(mobile): add QR scanner screen and hook coverage

PR Description
Summary
This PR adds the missing mobile QR scanner screen and hook coverage for the SwiftChain frontend.

What was implemented
Added the mobile QR scanner screen UI with:
permission loading state
live camera feed
retry flow for camera access errors
successful scan result overlay
manual tracking-code fallback
offline watermark state
Added the mobile QR scanner hook to handle:
camera start/stop logic
permission errors
QR verification request flow
scan result storage
Added the API service layer for QR verification
Added the supporting TypeScript model for scanned delivery data
Test coverage
Added focused unit tests covering:

permission loading state
camera error state with retry button
successful QR scan result display
manual entry flow
offline watermark rendering
hook-level scan and permission handling
Verification
Ran:
cd "/home/semicolon/Desktop/TechBroAfrica Drip/SwiftChain_Frontend" && npm test -- --runInBand components/mobile/tests/QrScannerScreen.test.tsx

Result:

1 test suite passed
9 tests passed
0 failed
Closes
Closes #[issue_id]

If you want, I can also tailor this into a more polished GitHub PR format with a checklist and a shorter “What Changed / Why / Validation” structure.

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