Create analytics-router.ts with ~30 tRPC endpoints for KPI management, alert
rules, scheduled reports, cohort analysis, and NPS survey integration.
Register router in index.ts under 'analytics' namespace. Fix pre-existing
bugs in service files: snake_case to camelCase conversion, missing non-null
assertions, and incorrect DB access patterns.
Co-Authored-By: Paperclip <noreply@paperclip.ing>