id: PORT-003
title: Historical LTV Chart
status: backlog
priority: P2
effort: M
depends_on:
  - PORT-001
tags: [portfolio, history, charts]
summary: Record and display historical LTV snapshots.
acceptance_criteria:
  - Store LTV snapshots over time.
  - Display 7/30/90 day charts with the margin threshold line.
  - Allow export as CSV.