The time-in-range labels in the doctor report, the target caption on
the glucose panel, the glucose page description and the fasting
explainer printed fixed mg/dL figures, so a reader on mmol/L saw
"Low (< 70 mg/dL)" beside values in mmol/L.
The cut-points now live in one place (`GLUCOSE_TIR_CUT_POINTS`,
`GLUCOSE_FASTING_CUT_POINTS`) with the SI figure each guideline prints,
the analytics engine counts its bands from the same constants, and
every sentence takes the band edges and unit as parameters through
`glucoseBandParams`, formatted with the reader's number format.
The unit-preference guard now also reads the locale bundles: a string
that names mg/dL or mmol/L fails unless it is allowlisted with a
reason.
Refs #1067