Vitamin D rendered as 'VitaminDIU' with no unit — strippedSuffix table has 'UI' instead of 'IU' #40

cmd/format.go::strippedSuffix has the suffix table:

{"Kcal", "kcal"},
{"Mg",   "mg"},
{"Ug",   "µg"},
{"UI",   "IU"},
{"G",    "g"},

But the struct field is VitaminDIU (ends in IU, not UI) — standard international-units abbreviation:

// internal/cronoapi/records.go:65
VitaminDIU       float64 \`json:"VitaminDIU"\`

So the "UI" entry never matches, and strippedSuffix("VitaminDIU") returns ("VitaminDIU", "") — markdown renders without a unit and without splitting the name. Reproduced standalone:

VitaminDIU           -> "VitaminDIU"  unit=""
VitaminAUg           -> "VitaminA"    unit="µg"
VitaminCMg           -> "VitaminC"    unit="mg"

Real-world impact: any markdown serving with non-zero vitamin D shows up as

- VitaminDIU: 123

instead of

- VitaminD: 123 IU

Fix: change the table entry to {"IU", "IU"}. (No other field ends in UI, so the old entry was dead code from the start.) Add a unit test for strippedSuffix covering one field per suffix — would have caught this on day one.

Severity: minor (cosmetic, but visible to every user with vitamin D logged)