Keep the main docker run command front and center. Lite and CUDA
variants are in a collapsible details block so the quick start
section stays scannable.
SVG files were rejected by the convert endpoint because
validateImageBuffer only recognized raster magic bytes. This adds
text-based SVG detection, sanitization in the tool factory, and
proper Sharp density handling so SVG-to-raster conversion works
through the standard convert route.
test-200x150.png and test-1x1.png were present locally but never
committed, causing CI failures on clean checkouts. Also added a
gitignore exception for tests/fixtures/*.png.