Implement background sync dashboard for mobile offline queue

[inteee]

Description

If offline drafts exist, operators need visibility into pending, failed, and synced mobile actions.

Scope

• Add mobile sync status screen
• Show pending vitals and notes with timestamps
• Support retry and discard actions
• Keep local-only management simple

Acceptance Criteria

• Mobile app shows pending and failed sync items
• User can retry failed sync attempts
• Synced items are removed or archived from pending queue

Dependencies

Blocked by #225
Blocked by #226

Stack

React Native