Show estimated HbA1c in mmol/mol (IFCC) alongside the % value

Dutch lab results conventionally report HbA1c in mmol/mol rather than
DCCT/NGSP %. Adds gmi_mmol_per_mol() using the standard IFCC conversion
(Hoelzel et al. 2004) and shows it next to the existing % value on the
Samenvatting page and in the PDF summary.

Closes gitea #25.

pages/2_Samenvatting.py

@@ -4,6 +4,7 @@ import streamlit as st
 from auth import require_auth
 from nightscout_client import NightscoutConfigError
 from reporting import (
+    gmi_mmol_per_mol,
     gmi_percent,
     percent_cv,
     sensor_active_percent,
@@ -43,6 +44,7 @@ active_pct = sensor_active_percent(glucose, start, end)
 
 mean_mmol = glucose["mmol"].mean()
 gmi = gmi_percent(mean_mmol)
+gmi_mmol_mol = gmi_mmol_per_mol(gmi)
 cv = percent_cv(glucose)
 tir = tir_breakdown_5band(glucose)
 
@@ -50,7 +52,11 @@ st.subheader("Kerncijfers")
 col1, col2, col3, col4 = st.columns(4)
 col1.metric("Sensordekking", f"{active_pct:.0f}%", help="Streefwaarde: ≥70%")
 col2.metric("Gemiddelde glucose", f"{mean_mmol:.1f} mmol/L")
-col3.metric("Geschat HbA1c (GMI)", f"{gmi:.1f}%", help="Bergenstal et al. 2018 — geen labwaarde")
+col3.metric(
+    "Geschat HbA1c (GMI)",
+    f"{gmi:.1f}% ({gmi_mmol_mol:.0f} mmol/mol)",
+    help="Bergenstal et al. 2018 — geen labwaarde",
+)
 col4.metric("Variabiliteit (%CV)", f"{cv:.0f}%", help="Streefwaarde: ≤36%")
 
 st.subheader("Tijd in bereik (5 klinische banden)")