research: evaluate PostHog event taxonomy for dashboard user journeys

[basanth-p]

Summary

Define and document the PostHog event taxonomy for all key user journeys in the dashboard.

Journeys to map

1. Landing page → Connect → OAuth → Onboarding → Dashboard
2. Returning user → Dashboard → Score page
3. Share profile link flow
4. Settings / disconnect account

Deliverable

A documented event map in docs/analytics-events.md covering:

• Event name
• Trigger point
• Properties captured
• User identified or anonymous

Notes

ANALYTICS_EVENTS constants already exist in lib/analytics/events.ts — extend from there.