fix(labs): never present a converted reading's printed range in the wrong unit

A converted reading's bounds move with its value, but the printed range text
stays in the unit the report used, and every reader preferred that text: the
list showed "Report range 3.9 to 5.5" beside 100.9 mg/dL, and the doctor
report and the FHIR referenceRange.text did the same. The text is still
stored verbatim. The range resolver now takes the reading's sourceUnit (as a
required field, so no reader can forget to select it) and, for a converted
reading, leaves the window's text empty so every surface states the converted
bounds in the marker's unit, and hands the printed text over separately with
its unit. The lab DTO carries it as printedReferenceText, and the note beside
a reading shows it as "as printed in mmol/L: ...".

src/app/api/insights/labs-changes/route.ts

@@ -52,6 +52,7 @@ export const GET = apiHandler(async () => {
       sourceReferenceLow: true,
       sourceReferenceHigh: true,
       sourceReferenceText: true,
+      sourceUnit: true,
       takenAt: true,
     },
     orderBy: { takenAt: "desc" },
@@ -67,6 +68,7 @@ export const GET = apiHandler(async () => {
       sourceReferenceLow: r.sourceReferenceLow,
       sourceReferenceHigh: r.sourceReferenceHigh,
       sourceReferenceText: r.sourceReferenceText,
+      sourceUnit: r.sourceUnit,
       takenAt: r.takenAt,
     })),
   );