Remove leftover dev/test scaffolding files

[wrigjl]

During the Node 26 / package upgrade work on branch submit/node-update-26, we identified several files that appear to be leftover dev scaffolding with no production use. Proposing to delete them — wanted to check before doing so.

Files in question

File	Reason
pages/api/hello.js	Default Next.js scaffold ({ name: 'John Doe' }), not called by anything
pages/testvis.js	Dev test page, not linked from navigation or any other page
components/widgets/SearchBars/testAutoProb.js	Only imported by testvis.js and a commented-out line in navigationgraph/index.js
pages/Visualizations/quantum-demo.js	Standalone demo page with a hardcoded circuit, not linked from navigation

Also worth noting

pages/visualizer.js has const SHOW_QUANTUM_VIS = false and immediately returns null — effectively dead. May also be a candidate for removal or enabling.

Question

Are any of these intentionally kept (e.g. for demos, onboarding, or future use)? If not, we'd like to remove them as part of the cleanup PR.