The MCS-150 biennial update re-confirms the carrier's existing FMCSA
record. Previously the PDF filler only had whatever the intake form
collected; rescued/sparse orders (or orders where the carrier's data
lives in FMCSA, not the intake) produced near-empty forms. Now we pull
the carrier census (legal name, address, EIN, fleet counts) from the
FMCSA carrier API and merge it under any customer-provided intake values
(customer edits win), so the form is pre-filled with the carrier's
current registered data. Refactored the FMCSA fetch into a shared
_fetch_fmcsa_carrier helper used by both enrichment and status check.
