feat(PORT-003): add historical ltv charts

docs/roadmap/done/PORT-003-historical-ltv-chart.yaml

@@ -0,0 +1,19 @@
+id: PORT-003
+title: Historical LTV Chart
+status: done
+priority: P2
+effort: M
+depends_on:
+  - PORT-001
+tags:
+  - portfolio
+  - history
+  - charts
+summary: Workspace-scoped LTV snapshots are now recorded over time and rendered on the overview page with CSV export.
+completed_notes:
+  - Added structured workspace-scoped LTV snapshot persistence in `app/models/ltv_history.py`.
+  - Added chart-range and CSV export support in `app/services/ltv_history.py`.
+  - Updated `app/pages/overview.py` to record snapshots, display 7/30/90 day LTV charts with the margin threshold line, and expose `Export CSV`.
+  - Added focused regression coverage in `tests/test_ltv_history.py` for persistence, same-day replacement, range filtering, and CSV export.
+  - Added a Playwright regression test in `tests/test_overview_ltv_history_playwright.py` covering the exact changed route, live rendered chart series on the overview page, and CSV download path on `/{workspace_id}`.
+  - Manual local Docker validation confirmed the stack starts cleanly, `/health` returns OK, and the Docker-served overview route renders the LTV history UI without visible runtime errors.