MVP: Capture privacy-safe Talent Scout usage metrics

[andjump]

Context

See:

• docs/PRD.md §14 (Observability)
• docs/build-log.md (Success criteria)

We need to understand whether the Talent Scout is helping without storing sensitive data.

Task

Add analytics events for key Talent Scout interactions.

Suggested events:

• talent_scout_opened
• opportunities_recommended
• opportunity_clicked
• opportunity_saved
• feedback_submitted (thumbs up/down)

Acceptance criteria

• No raw conversation logs required for MVP
• Events are aggregated and privacy-safe
• Metrics can be reviewed by SBARC admins

Out of scope

• Full analytics dashboards
• Behavioural profiling