Sprint 6A: MVP web shell and core operator views

[samrusani]

Summary

• replace the placeholder Next.js landing page with the first real AliceBot operator shell
• add the in-scope /chat, /approvals, /tasks, and /traces views plus shared shell components
• keep the sprint within existing backend scope and use fixture-backed or existing-endpoint-backed data only

Verification

• npm run build in apps/web: PASS

Notes

• next build still causes local config churn in apps/web/tsconfig.json and apps/web/next-env.d.ts and those generated changes were reverted
• npm run lint is not yet a stable non-interactive check