feat: add Barcode and PackingList API client

[wakemeup0]

Summary

• Add BarcodingClient for product and pack list barcode lookups.
• Add PackingList v1 invoice, sales order, and PO lookups on the same client.

Test plan

• bun run check

[Copilot]

Pull request overview

Adds a new BarcodingClient to the SDK to expose Digi-Key Barcoding v3 barcode lookup endpoints and PackingList v1 lookup endpoints, and wires it into DigiKeyClient with generated OpenAPI-based types plus coverage to ensure paths/query mapping are correct.

Changes:

• Introduce BarcodingClient with product/packlist barcode lookups and PackingList invoice/sales-order/PO lookups.
• Attach the client on DigiKeyClient as client.barcoding and export the new client/types from the package entrypoint.
• Add Bun tests verifying request path/query construction and OAuth-flow configuration enforcement.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/barcoding.test.ts	Adds tests asserting endpoint-to-path/query mapping and OAuth-flow configuration validation.
src/index.ts	Re-exports Barcoding/PackingList client and related generated types from the public entrypoint.
src/constants.ts	Adds base path constants for Barcoding v3 and PackingList routing.
src/client.ts	Instantiates and exposes BarcodingClient via DigiKeyClient.barcoding.
src/barcoding.ts	Implements BarcodingClient methods and type aliases for Barcoding v3 + PackingList v1 operations.

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