Days before the first recorded day in history.daily were painted as a real
0.00/0 calls in the daily activity heatmap and the daily spend charts. That
zero is unknown, not measured, so those cells and bars now read "No data
recorded" instead of a currency zero. Genuinely idle days within recorded
history stay as real zeros.
- app: heatmap cells, the daily spend bars, and the daily-by-model columns
get a distinct no-data style plus a "No data recorded" hover for days before
the first recorded day.
- dash: the granular line chart drops buckets before the first recorded day so
no flat zero line is drawn before any history exists.
- data-start is derived in the UI layer from history.daily; payload shape is
unchanged.
Verified: app vitest 418 pass (7 new for the no-data behavior); app, dash, and
root typecheck clean; dash and app renderer vite builds succeed.
