Améliorations d'ergonomie et de code

src/data/coords/ellipseCoords.ts

src/data/coords/transform/ellipseFitter.ts

src/data/coords/transform/transformation.ts

src/data/dataExporter.ts

src/instruments/blobMask.ts

src/lab.tsx

src/steps/downloadStep.tsx

src/steps/drawBlobMaskStep.tsx

src/steps/placePetriDishStep.tsx

src/steps/rulerStep.tsx

src/steps/step.tsx