units.csv: two units have no QUDT reference while QUDT has them

In [`DataFiles/units.csv`](https://github.com/buildingSMART/bSDD/blob/master/DataFiles/units.csv)
(and the same in `api/Unit/v1`, checked 2026-09-11):

| units.csv | QUDT should be |
|---|---|
| `mm/m,millimetre per metre,NULL,NULL` | `MilliM-PER-M` |
| `m²·K/W,square metre kelvin per watt,NULL,NULL` | `M2-K-PER-W` |

Both resolve under http://qudt.org/vocab/unit/. I map units from an RDF source onto bSDD codes on
the QUDT reference first and fall back to the name; without the reference these two can only be
matched by name, which is what the QUDT column is there to prevent. 417 of the 616 units carry one.

Open DataFiles/units.csv and locate the rows for mm/m and m²·K/W. Verify their QUDT unit references against the identifiers in the issue, then check the corresponding api/Unit/v1 data noted there. Done means both units carry the correct QUDT references in each stated location.

Written by the indexing model from the issue text.