ACCS-871: Add Error State Handling on /pay Page

[yutingjiangYTJ]

Please always provide the GitHub issue(s) your PR is for, as well as test URLs where your change can be observed (before and after):

Fix #

Test URLs:

• Before: https://main--aem-boilerplate-commerce--hlxsites.aem.live/
• After: https://ACCS-871--aem-boilerplate-commerce--hlxsites.aem.live/

Ticket:
https://jira.corp.adobe.com/browse/ACCS-871

Changes

Shared error modules in blocks/commerce-pay-by-link/errors/:

• error-states.js — 9 states, backend code + HTTP status mapping (404/409/410), resolveOnRetry()
• error-card.js — accessible error UI (role="alert", focus management, Elsie Button CTAs), plus renderMappedError() for API failures
• Block integration:
  • Pre-flight errors (missing/malformed token) → renderErrorCard()
  • payByLinkOrder failures → renderMappedError() with automatic retry for generic errors
• i18n via PayByLink.* da.live placeholders (including ErrorGenericTitle / ErrorGenericBody / ErrorTryAgainLabel)
• Cypress E2E: verifyPayByLinkPageShell, verifyPayByLinkOrderSummary, verifyPayByLinkErrorStates (not-found, expired, already-completed, generic + retry)
• Block README documenting states, exports, and i18n keys

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Commits

• 5791bc4 🔄 (latest)
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[github-actions]

📝 Block Changes Detected

This PR contains changes to the following blocks:

• ✅ blocks/commerce-pay-by-link/ (has README.md)
• ✅ blocks/commerce-pay-by-link-confirmation/ (has README.md)

📋 README Requirements

Please ensure the README.md for each changed block includes:

• Overview: Clear description of the block's purpose and functionality
• Configuration: All configuration options, their types, defaults, and side effects
• Integration: URL parameters, localStorage usage, and event handling
• Behavior Patterns: User interaction flows and page context detection
• Error Handling: How the block handles errors and fallback scenarios

✅ All blocks have README files

Please review and update the README files to ensure they accurately reflect any changes made to the blocks.

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