Add Scanfile official brand SVGs

[taosz]

Adds Scanfile, an online file-translation service, using its existing first-party brand assets.

• Adds the required 64×64 icon and 120×60 rectangle.
• Preserves the original path geometry, colors and outlined wordmark; only the viewBox and layout dimensions change.
• Adds metadata with the website and official logo-source URL.

Sources: symbol, lockup. Original logo rights remain with their owner, as described in this repository's README.

Validation: fflint v0.0.23 passed both SVG dimension checks and the repository's metadata schema/key-order check. Rendered output was also inspected.

• Images follow the current formatting guidelines.

Repository CI: icon dimensions, rectangle dimensions, filename checks and image checks pass. The full-repository metacheck fails parsing the pre-existing src/content/logos/gnupg/index.md; that file has the same blob (5559001a96ef63ec3bcea87b3a3b49fc22fe64bd) at the base and PR head. The new Scanfile metadata passes the native validator/schema check. This PR changes only the three Scanfile files.