Restore the original LeetTutor UX online

[widmonstertony]

What changed

• replace the separate hosted workspace with a thin bilingual connection shell
• embed the unchanged original Streamlit app from loopback port 8501
• make the companion launchers start app.py in hosted/headless mode
• preserve the floating JARVIS, split workspace, editor, progress, model settings, and mobile UX from the original source
• document that web-demo must never become a second product UI again

Root cause

The hosted client had been implemented as a separate static dashboard, so its information architecture and fixed JARVIS pane drifted from the original Streamlit product.

Impact

Users keep tonytan.me/leetcode/ as the browser entry while the actual product UI and all private execution remain on their computer. No code, prompts, progress, or model traffic reaches EC2.

Validation

• node --check web-demo/app.js
• python -m compileall -q app.py leettutor scripts tests
• python -m pytest -q (100 passed, 3 subtests)
• Chrome visual verification of the embedded original app and floating JARVIS