feat(analytics-studio): Power BI-inspired local dashboards

Summary

Adds src/analytics-studio/ — aggregates, KPI/bar widgets over seeded rows. No LIVE warehouse. Amplify/README + icons.

DOCUMENTED vs LIVE

See src/analytics-studio/README.md — honest comparison; no fabricated LIVE access.

Test plan

• cd src/analytics-studio && npm ci && npm test && npm run build (4 tests)
• Smoke the UI