Add loading states and disable buttons during API calls

[StencilwashCoder]

Problem

Currently users can tap buttons multiple times while API calls are in flight. No visual feedback shows that an operation is pending.

Affected Screens

• • no loading state during check-in API call
• (if exists) - can create multiple shifts
• (if exists) - can submit lot multiple times
• (if exists) - payroll could run twice = double pay

Current Code Example

The state exists but:

• Button doesn't show spinner
• Scanner isn't visually disabled
• User can still navigate back and lose the pending operation

Implementation

Update Button Component

Update Screens

• - disable scanner + show loading overlay during check-in
• - disable create button, show spinner
• - disable submit, show spinner
• - CRITICAL: show big warning + spinner, disable all actions

Add Loading Overlay Component

Prevent Double-Submit Pattern