[MEDIUM] Add mobile service layer and offline sync tests

[kilodesodiq-arch]

Engineering Gap

Mobile tests at app/mobile/src/__tests__/ cover render-only component tests. No tests for API service layer (api.ts, aidApi.ts), offline sync queue (syncQueue.ts), notification service, or cache services.

Codebase Evidence

• app/mobile/src/__tests__/: 11 test files — all component render tests
• app/mobile/src/services/api.ts: fetch-based API client with no test coverage
• app/mobile/src/services/syncQueue.ts: Offline queue with no test
• app/mobile/src/services/aidCache.ts: Cache logic with no test

Risk Profile

Current Risk

Offline sync failures in field operations undetected.

Business Impact

Field operators unable to submit claims offline. Aid distribution delayed.

Remediation Strategy

Add unit tests for API client with mocked fetch. Test sync queue with network on/off simulation. Test cache TTL and invalidation.

Success Conditions

• API client tests with mocked fetch
• Sync queue tests with network state changes
• Cache TTL and invalidation tests

Change Surface

New test files in app/mobile/src/__tests__/ for services

Security Review

No security impact.

Completion Checklist

• Implementation completed
• Peer reviewed
• Tests passing
• Ready for merge

[brentthomas248]

I submitted PR #207 for this issue: #207

The change adds focused mobile service-layer and offline-sync coverage for the listed success conditions: mocked aid API tests, AsyncStorage cache timestamp/invalidation tests, and sync-queue online/offline/retry/saver-mode tests. Targeted verification is included in the PR body.