feat(glucose): read glucose in one unit across series, CSV, and detail page

Glucose is stored canonical mg/dL but the series DTO, CSV export, and detail
page emitted raw mg/dL while FHIR already converted to the user preference.

Convert at serialization through the single convertGlucose helper:
- series route sets unit from the user's glucoseUnit and converts each point
- CSV export converts BLOOD_GLUCOSE rows and emits the unit in the unit column
- the detail page + stat strip honour the preference via the chart value scale
- declare the trailing-90-day window in the glucose median label across locales

mmol/L-preference users now see the blood-glucose page, stat strip, iOS series,
and CSV in mmol/L; mg/dL users are unchanged.

src/app/api/export/__tests__/per-type-routes.test.ts

@@ -135,6 +135,66 @@ describe("GET /api/export/measurements", () => {
       }),
     );
   });
+
+  // v1.16.16 — glucose unit-at-source. A mmol/L-preference user's CSV emits
+  // BLOOD_GLUCOSE converted (100 → 5.5) with `mmol/L` in the unit column.
+  it("exports BLOOD_GLUCOSE in the user's mmol/L preference", async () => {
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    vi.mocked(checkRateLimit).mockResolvedValue({
+      allowed: true,
+      remaining: 9,
+      resetAt: Date.now() + 3600_000,
+    });
+    vi.mocked(prisma.user.findUnique).mockResolvedValue({
+      glucoseUnit: "mmol/L",
+    } as never);
+    vi.mocked(prisma.measurement.findMany).mockResolvedValue([
+      {
+        type: "BLOOD_GLUCOSE",
+        value: 100,
+        unit: "mg/dL",
+        measuredAt: new Date("2026-05-01T08:00:00.000Z"),
+        source: "MANUAL",
+        notes: null,
+        glucoseContext: "FASTING",
+      },
+    ] as never);
+
+    const { GET } = await import("../measurements/route");
+    const res = await GET(mkReq("http://localhost/api/export/measurements"));
+    expect(res.status).toBe(200);
+    const body = await res.text();
+    expect(body).toContain("BLOOD_GLUCOSE,5.5,mmol/L");
+    expect(body).not.toContain("100,mg/dL");
+  });
+
+  it("exports BLOOD_GLUCOSE in raw mg/dL for a mg/dL-preference user", async () => {
+    vi.mocked(getSession).mockResolvedValue(SESSION_OK as never);
+    vi.mocked(checkRateLimit).mockResolvedValue({
+      allowed: true,
+      remaining: 9,
+      resetAt: Date.now() + 3600_000,
+    });
+    vi.mocked(prisma.user.findUnique).mockResolvedValue({
+      glucoseUnit: "mg/dL",
+    } as never);
+    vi.mocked(prisma.measurement.findMany).mockResolvedValue([
+      {
+        type: "BLOOD_GLUCOSE",
+        value: 100,
+        unit: "mg/dL",
+        measuredAt: new Date("2026-05-01T08:00:00.000Z"),
+        source: "MANUAL",
+        notes: null,
+        glucoseContext: "FASTING",
+      },
+    ] as never);
+
+    const { GET } = await import("../measurements/route");
+    const res = await GET(mkReq("http://localhost/api/export/measurements"));
+    const body = await res.text();
+    expect(body).toContain("BLOOD_GLUCOSE,100,mg/dL");
+  });
 });
 
 describe("GET /api/export/medications", () => {

src/app/api/export/measurements/route.ts

@@ -25,6 +25,7 @@ import { checkRateLimit } from "@/lib/rate-limit";
 import { toCSV, formatMeasurementsForExport } from "@/lib/export";
 import { resolveUserTimezone } from "@/lib/tz/resolver";
 import { loadUserSourcePriority } from "@/lib/rollups/measurement-read";
+import { resolveGlucoseUnit } from "@/lib/glucose";
 import { NextRequest, NextResponse } from "next/server";
 
 export const GET = apiHandler(async (request: NextRequest) => {
@@ -45,20 +46,29 @@ export const GET = apiHandler(async (request: NextRequest) => {
       ? "raw"
       : "night";
 
-  const [measurements, userTz, sourcePriorityJson] = await Promise.all([
-    prisma.measurement.findMany({
-      where,
-      orderBy: { measuredAt: "desc" },
-    }),
-    resolveUserTimezone(user.id),
-    loadUserSourcePriority(user.id),
-  ]);
+  const [measurements, userTz, sourcePriorityJson, profile] =
+    await Promise.all([
+      prisma.measurement.findMany({
+        where,
+        orderBy: { measuredAt: "desc" },
+      }),
+      resolveUserTimezone(user.id),
+      loadUserSourcePriority(user.id),
+      // v1.16.16 — resolve the glucose display unit so BLOOD_GLUCOSE rows
+      // export in the user's unit (matching FHIR), not raw stored mg/dL.
+      prisma.user.findUnique({
+        where: { id: user.id },
+        select: { glucoseUnit: true },
+      }),
+    ]);
+  const glucoseUnit = resolveGlucoseUnit(profile?.glucoseUnit ?? null);
 
   const csv = toCSV(
     formatMeasurementsForExport(measurements, userTz, {
       granularity,
       sleepTz: userTz,
       sourcePriorityJson,
+      glucoseUnit,
     }),
   );