IronShell: STL repair

Upload a broken STL, get back one that’ll actually print. The repair engine names and fixes the specific ways a mesh lies about being solid (holes, non-manifold edges, inverted normals, degenerate faces, self-intersections) and lets you choose the goal: preserve geometry, optimize printability, or minimize triangles. It’s built as a real pipeline, with a Postgres-backed job queue, S3 for the files, batch jobs, and a Kubernetes deployment, plus a touch I like where the API returns the indices of every face it modified so the frontend can highlight the repairs like a diff.