BE026 - Durable Shopping-List Offline Outbox and Reconciliation

[lindahha]

Ticket

BE026 - Durable Shopping-List Offline Outbox and Reconciliation

• BE026

Description

Implemented offline outbox support for shopping list synchronization.

• Added a local shopping list outbox for queuing pending sync operations.
• Added support for retrying failed synchronization operations.
• Added shopping list sync state tracking for pending, failed, and synced operations.
• Integrated the outbox and sync state into the shopping list hook.
• Added automated tests covering outbox queuing, pending operations, retries, failures, and sync state.

Testing

cd mobile-app
npx jest __tests__/shoppingListOutbox.test.ts --runInBand

Result: 8 tests passed, 1 test suite passed.


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## Checks 

- [x] All requirements of the ticket have been implemented, or I have commented on any exclusions
- [x] Unit tests have been added or updated for any backend changes (if applicable)
- [x] I have reviewed the **Files Changed** tab and verified it only contains relevant changes (comment if unsure about any)
- [ ] This PR has been reviewed and approved


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