fetch_users/fetch_tickets were placeholder stubs returning empty
lists, so the generated Excel was always empty. Wire them to the
existing utils.accounts_client / utils.advertising_client integrations
(same ones the bundled-zip report on master uses), and update
UserReport/TicketsReport to the real Account/Ticket field names
instead of the old mock dict shape. Drop the now-unused local OAuth
helper in favor of each client's own client-credentials flow.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Restore the original report_type-driven endpoint (users/tickets picked
individually via serializer + orchestrator) that was replaced by the
bundled zip export in b293509, on top of current master.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
