build(deps): bump vite to ^8 and @vitejs/plugin-react to ^6

[ivostoynovski]

Summary

• Combined bump of vite (6 → 8) and @vitejs/plugin-react (4 → 6) — they have a mutual peer-dep constraint and must land together
• Replaces build(deps-dev): bump vite from 6.4.2 to 8.0.12 #22 (vite alone) and build(deps-dev): bump @vitejs/plugin-react from 4.7.0 to 6.0.1 #21 (plugin-react alone), both of which failed CI on their own
• Verified locally with npm run build

Test plan

• npm install resolves cleanly (no ERESOLVE)
• npm run build succeeds
• Verify dev server (npm run dev) still works
• Re-deploy and smoke-test the site

🤖 Generated with Claude Code