Inspired by the user's "Journey to £1M" reference — adds vertical
dashed lines on every timeseries panel at the date net worth first
crossed each round threshold (£100k, £250k, £500k, £750k, £1M).
Implementation: a dashboard-level annotation source ("Milestones",
purple) backed by a PG query that finds the MIN(valuation_date) where
SUM(total_value) >= each threshold. The query returns (time, text)
pairs, e.g. "2026-04-18 → £1M 🎉". Annotations attach to all
timeseries panels automatically; auto-extends as future thresholds
are crossed.
Verified against current data:
£100k → 2021-11-01 £250k → 2023-07-18 £500k → 2024-09-19
£750k → 2025-08-26 £1M → 2026-04-18 🎉
Future work (per user request): add a "Journey" stat-card row at the
top mirroring the reference (date achieved + months from previous).