Refactor Pages dashboard to React

[samsnowy]

Summary

• Move the GitHub Pages dashboard into a Vite/React app under site/
• Build the static React output into docs/ for Pages
• Have python main.py export write docs/data.js and run the React build
• Keep the current portfolio snapshot available to the dashboard via window.TMC_DATA

Verification

• python -m py_compile main.py congress/live.py config.py
• npm run build