Retrieves a per-day breakdown of cost and credits applied for the authenticated user's
organization, grouped by (date, provider, model).

Returns a flat list of rows (one per date × provider × model) plus organization-wide
envelope totals. Suitable for timeseries charts and burn-down analyses.

All costs and credits are in USD. creditsApplied is null on rows where no credits data
is available. The envelope totalCreditsApplied is null only when no row in the page
has a non-null value.