Add SAMRI icon and SVG icon sync

[stebo85]

Summary

• Add generated SAMRI PNG icon from the upstream SVG recipe icon
• Teach the neurocontainer icon sync helper to rasterize SVG data URIs with cairosvg
• Install cairosvg in icon sync, apps.json queue, and unit-test workflows
• Remove trailing bytes from two PNG icons

Validation

• pytest -q
• python .github/workflows/scripts/sync_neurocontainer_icons.py --neurocontainers-path ../neurocontainers --icons-dir neurodesk/icons --apps-json neurodesk/apps.json --check
• PNG trailing-byte audit