feat(blocks): add Brand Kit logo variation

[TheAggressive]

Summary

• classify Logo as a constrained WordPress Core Image variation backed by one read-only Brand Kit binding source
• version the Brand Kit asset snapshot and import an HTTPS raster Site Logo with alt text, intrinsic dimensions, and an optional homepage link
• resolve the frozen logo deterministically through the existing image renderer with bounded proportional dimensions
• cover editor serialization, compiler failures, client structure, persistence, and package output

Classification

Logo uses core/image plus campaignbridge/brand-data. CampaignBridge does not register a duplicate Logo block or a second asset store. Theme import copies the current Site Logo into Brand Kit version 3, and compilation never reads live theme or Media Library data.

Validation

• pnpm build
• pnpm qa:fast
• pnpm test — 1,132 tests, 5,305 assertions
• pnpm exec playwright test tests/e2e/brand-logo.spec.ts
• pnpm release:package && pnpm release:verify

Refs #96