Implement order, checkout, and basket operations views

[juliuskrah]

Parent initiative: #287

Summary

Implement order, checkout, and basket operation views in the commerce admin for operational support workflows.

Acceptance criteria

• Order, checkout session, and basket lists load from GraphQL with context-aware filters and pagination.
• Detail views show customer, line item, ProductVariant, payment handoff, fulfillment-relevant status, and timeline data where the API exposes it.
• Unavailable backend capabilities render planned or blocked states without mocking successful operations.
• Loading, empty, not found, unauthorized, and API error states are visible and recoverable.
• Unit/component tests and available Playwright coverage exercise list, detail, filter, and error workflows.

Architecture note

gitstore-admin remains an optional add-on and consumes gitstore-api; it must not talk directly to gitstore-git-service.