Trend charts (MTU + calls) in project view

[axelgar]

Parent

PRD-v2/C · Observability (Phase 1) — PRD-v2c-observability.md

What to build

Surface usage history in the dashboard project view as two line charts — MTU over time and calls over time — reading from the usage_snapshots table. Charts cover period-to-date plus trailing history, with period boundaries aligned to the billing period the meter already uses. The dashboard is already Tailwind v4 + shadcn; lean minimal (ponytail) — hand-rolled SVG or a small charting primitive, no heavy dependency unless the simple version visibly fails.

Acceptance criteria

• Project view renders an MTU-over-time line chart and a calls-over-time line chart from snapshot data
• Charts show the available history (graceful when only a few days exist)
• Period boundaries align with the meter's billing period
• No heavy charting dependency added unless a minimal SVG/primitive approach demonstrably falls short

Blocked by

• usage_snapshots table + daily snapshot cron #3 (needs persisted snapshots to chart)