feat(withings): ingest meastype 123 (VO2 max) into VO2_MAX

The ScanWatch family reports VO2 max under meastype 123 in
mL/(kg·min), which matches HealthLog's canonical DB unit verbatim
(no conversion needed beyond the standard value × 10^unit exponent
decode). Targets the VO2_MAX enum slot added in v1.4.23 for the
Apple Health passthrough.

src/lib/withings/__tests__/client.test.ts

@@ -64,6 +64,20 @@ describe("MEASURE_TYPE_MAP", () => {
   it("maps Withings meastype 35 (legacy SpO2) → OXYGEN_SATURATION", () => {
     expect(MEASURE_TYPE_MAP[35]).toEqual({ type: "OXYGEN_SATURATION" });
   });
+
+  it("maps Withings meastype 123 (VO2 max) → VO2_MAX", () => {
+    expect(MEASURE_TYPE_MAP[123]).toEqual({ type: "VO2_MAX" });
+  });
+});
+
+describe("fetchMeasurements — VO2 max (meastype 123)", () => {
+  it("decodes a ScanWatch VO2 max reading into VO2_MAX mL/(kg·min)", async () => {
+    // 42.5 mL/(kg·min) as Withings exponent encoding: value=425, unit=-1.
+    installFetchMock(fakeGetmeasPayload([{ type: 123, value: 425, unit: -1 }]));
+    const out = await fetchMeasurements("token");
+    expect(out).toHaveLength(1);
+    expect(out[0]).toMatchObject({ type: "VO2_MAX", value: 42.5 });
+  });
 });
 
 describe("fetchMeasurements — SpO2 alt code (meastype 35)", () => {

src/lib/withings/client.ts

@@ -142,6 +142,9 @@ export const MEASURE_TYPE_MAP: Record<number, { type: string; factor?: number }>
   // SpO2 under meastype 35 instead of 54. Both target OXYGEN_SATURATION
   // in percent; the exponent decode handles 0.97 vs 97 transparently.
   35: { type: "OXYGEN_SATURATION" },
+  // v1.4.25 — VO2 max from the ScanWatch family. Withings reports
+  // mL/(kg·min) directly, matching the canonical DB unit.
+  123: { type: "VO2_MAX" },
 };
 
 export interface WithingsMeasure {