WooPOS: Add shimmer loading to refund dialog

[samiuelson]

WOOMOB-1861

Description

1. The refund dialog's loading state previously showed a plain spinner (LoadingContent), which caused a jarring visual jump when transitioning to the item selection screen. This PR replaces it with a shimmer skeleton that mirrors the real SelectItemsContent layout, and improves the confirm step's processing state.
2. It replaces spinner also in the "Confirm Refund" step, by using loading button state.
3. Animations have been added to make transitions between dialog steps smooth.

Changes:

• Widen SelectItemsContent to accept WooPosRefundState (not just Content), rendering shimmer item rows when state is Loading
• Remove the separate LoadingContent spinner composable
• Show the close (X) button during loading so users can dismiss the dialog early
• Add AnimatedContent fade transitions between refund dialog states and between refund steps
• Use WooPosButton loading state instead of a standalone spinner during refund confirmation — the "Yes, proceed" button now shows a built-in spinner while "Back" is disabled

Test Steps

1. Open an order and tap "Issue Refund"
2. Verify a shimmer skeleton appears (header, shimmer item rows, disabled button) while loading
3. Verify the refunds states transitions smoothly with animation
4. Select items and proceed to the confirm step — tap "Yes, proceed" and verify the button shows an inline loading spinner (not a standalone spinner replacing both buttons)
5. Verify the "Back" button is greyed out and non-clickable while processing
6. Complete a full refund flow (select items → review → confirm → success) and verify everything works

Images/gif

Screen_recording_20260313_182232.mp4

• I have considered if this change warrants release notes and have added them to RELEASE-NOTES.txt if necessary. Use the "[Internal]" label for non-user-facing changes.

[dangermattic]

	2 Warnings
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.
⚠️	This PR is assigned to the milestone 24.4. This milestone is due in less than 2 days. Please make sure to get it merged by then or assign it to a milestone with a later deadline.

Generated by 🚫 Danger

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce Android by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce Android
	Platform	📱 Mobile
	Flavor	Jalapeno
	Build Type	Debug
	Build Number	734
	Version	24.3-rc-3
	Application ID	com.woocommerce.android.prealpha
	Commit	d84822f
	Installation URL	41laujmo6kds0

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 162 lines in your changes missing coverage. Please review.
✅ Project coverage is 39.58%. Comparing base (d0f562e) to head (d84822f).
⚠️ Report is 8 commits behind head on trunk.

Files with missing lines	Patch %	Lines
...s/orders/details/refund/WooPosIssueRefundDialog.kt	0.00%	162 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##              trunk   #15538      +/-   ##
============================================
- Coverage     39.60%   39.58%   -0.02%     
  Complexity    11267    11267              
============================================
  Files          2253     2253              
  Lines        130170   130233      +63     
  Branches      18241    18252      +11     
============================================
  Hits          51552    51552              
- Misses        73349    73412      +63     
  Partials       5269     5269              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[kidinov]

LGTM, thanks!

I would just make:

• Check box make slightly smaller
• And the name of a product maybe a bit longer
• We need to have a separator in between of the items to mimic the items in refund list

EDIT: Done in 742c7eb ☝️