Returns a paginated list of per-user dispatches across all communications of
the authenticated tenant within a date range. Includes dispatches sent via
mass communications and via /communication/easy-send.

Use the communicationId filter to narrow the result to a single mass
communication (segment schedule); dispatches created by easy-send have
communicationId = null and cannot be filtered by it.

Limits

• The date range must not exceed 7 days.
• endDate must be greater than or equal to startDate.
• Both dates are normalized to full-day boundaries on the server
  (startDate → start of day, endDate → end of day).