✨ feat(availability): deprecate AvailabilityContainer and make standalone component

[acasazza]

Summary

Do the same changes done for Prices and Skus: deprecate AvailabilityContainer and make the Availability component standalone, so it can fetch data without requiring a container parent.

Work

• Deprecate <AvailabilityContainer> (keep backwards-compatible)
• Make <Availability> standalone — accepts skuCode prop and auto-fetches availability without a container
• Reuse/extend the shared createBatchStore pattern from @commercelayer/core if batching is needed, or use SWR-based single-item fetching (similar to useSkuList)
• Update useAvailability hook if needed
• Update docs/stories with standalone usage examples

Reference

• Same pattern as <Sku> standalone (✨ feat(skus): standalone Sku component, deprecate SkusContainer, shared debounce batch store #757)
• Same pattern as <SkuList> standalone (✨ feat(skus): standalone Sku component, deprecate SkusContainer, shared debounce batch store #757)
• createBatchStore already available in @commercelayer/core