QR placeholder source provenance

These three SVG files are copied byte-for-byte from the existing frontend at:
frontend-customizer-designer/frontend/public/assets/qr/

The frontend qrCodeList.js binds their names to numeric imageId values 2, 3 and 4.
They preserve the authored QR logo placeholder dimensions and transparency.
SavedProjectInput verifies their SHA-256 before granting them to an immutable job.
They inherit the licensing/provenance of those existing project assets; this file
introduces no separate third-party license claim.
