VCST-5769-vcst-qa-deployment

[vc-ci]

ci: Automated update vc-frontend from PR 2456 VirtoCommerce/vc-frontend#2456

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Note

Low Risk
Single deployment pointer change with no auth or business-logic edits; wrong URL would only affect which theme package is deployed to the QA environment.

Overview
Updates theme/artifact.json to point QA/theme deployment at a new prerelease package from vc-frontend PR 2456, replacing the previous PR 2436 zip (vc-theme-b2b-vue-2.57.0-pr-2456-7564-7564c89a.zip).

Pushes on vcst-* branches that touch theme/** will read this URL in deploy-theme.yml and set the cloud theme parameter for B2B-store, so this change only affects which theme bundle gets deployed—not application code in this repo.

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