feat(dashboard): VO2 max trend tile (opt-in, secondary-metric pattern)

Adds the VO2 max strip tile to /, matching the existing
secondary-metric convention (sleep / steps / glucose / oxygen
saturation are all default-invisible + opt-in via Settings →
Dashboard).

Wire-up:
  - src/lib/dashboard-layout.ts: vo2Max appended to
    DASHBOARD_WIDGET_IDS and DEFAULT_DASHBOARD_LAYOUT.widgets with
    visible=false / tileVisible=false. The /api/dashboard/widgets
    Zod enum is derived from the same array so the toggle is wired
    automatically.
  - src/app/page.tsx: vo2Summary from data?.summaries?.VO2_MAX
    (auto-populated by /api/analytics; the route iterates the full
    measurementTypeEnum.options list, no backend change needed),
    hasVo2 data-floor gate, showVo2Tile combined gate, and the
    TrendCard push next to showStepsTile. directionSentiment is
    up-good (higher VO2 max is better) and the unit string runs
    through the t() helper so the iOS app session can localise it.
  - src/components/settings/dashboard-layout-section.tsx: vo2Max
    label key added to WIDGET_LABEL_KEYS so the Settings → Dashboard
    toggle row renders the localized label.
  - messages/{en,de,fr,es,it,pl}.json: dashboard.vo2Max + vo2MaxUnit
    keys. "VO₂ max" is universal across all six locales (scientific
    abbreviation, no translation needed); the unit string is
    consistent SI notation.

No chart-row card — that's an explicit v1.5 deferral per the W8d
outline §6.4. The tile lights up the moment the user accumulates any
VO2 sample (Withings ingest or the upcoming iOS Health passthrough).

messages/de.json

@@ -247,6 +247,8 @@
     "bodyFat": "Körperfett",
     "sleep": "Schlaf",
     "steps": "Schritte",
+    "vo2Max": "VO₂ max",
+    "vo2MaxUnit": "mL/(kg·min)",
     "bpInTarget": "BD im Zielbereich",
     "days30Short": "30T",
     "medications": "Medikamente",

messages/en.json

@@ -247,6 +247,8 @@
     "bodyFat": "Body Fat",
     "sleep": "Sleep",
     "steps": "Steps",
+    "vo2Max": "VO₂ max",
+    "vo2MaxUnit": "mL/(kg·min)",
     "bpInTarget": "BP in Target",
     "days30Short": "30d",
     "medications": "Medications",

messages/es.json

@@ -247,6 +247,8 @@
     "bodyFat": "Grasa corporal",
     "sleep": "Sueño",
     "steps": "Pasos",
+    "vo2Max": "VO₂ max",
+    "vo2MaxUnit": "mL/(kg·min)",
     "bpInTarget": "BP in Target",
     "days30Short": "30d",
     "medications": "Medicamentos",

messages/fr.json

@@ -247,6 +247,8 @@
     "bodyFat": "Masse grasse",
     "sleep": "Sommeil",
     "steps": "Pas",
+    "vo2Max": "VO₂ max",
+    "vo2MaxUnit": "mL/(kg·min)",
     "bpInTarget": "BP in Target",
     "days30Short": "30d",
     "medications": "Médicaments",

messages/it.json

@@ -247,6 +247,8 @@
     "bodyFat": "Massa grassa",
     "sleep": "Sonno",
     "steps": "Passi",
+    "vo2Max": "VO₂ max",
+    "vo2MaxUnit": "mL/(kg·min)",
     "bpInTarget": "BP in Target",
     "days30Short": "30d",
     "medications": "Farmaci",

messages/pl.json

@@ -247,6 +247,8 @@
     "bodyFat": "Tkanka tłuszczowa",
     "sleep": "Sen",
     "steps": "Kroki",
+    "vo2Max": "VO₂ max",
+    "vo2MaxUnit": "mL/(kg·min)",
     "bpInTarget": "BP in Target",
     "days30Short": "30d",
     "medications": "Leki",

src/app/page.tsx

@@ -7,6 +7,7 @@ import {
   Activity,
   Droplet,
   Footprints,
+  Gauge,
   Heart,
   Moon,
   Percent,
@@ -251,6 +252,10 @@ export default function DashboardPage() {
   const bf = data?.summaries?.BODY_FAT;
   const sleepSummary = data?.summaries?.SLEEP_DURATION;
   const stepsSummary = data?.summaries?.ACTIVITY_STEPS;
+  // v1.4.25 W8d — VO2 max secondary-metric tile. /api/analytics
+  // auto-populates this summary because the route iterates over the
+  // full measurementTypeEnum.options list; no backend change needed.
+  const vo2Summary = data?.summaries?.VO2_MAX;
   const moodSummary = moodData?.summary;
 
   // Resolve full dashboard layout — controls visibility + order of every widget
@@ -307,6 +312,7 @@ export default function DashboardPage() {
   const hasMood = (moodSummary?.count ?? 0) > 0;
   const hasSleep = (sleepSummary?.count ?? 0) > 0;
   const hasSteps = (stepsSummary?.count ?? 0) > 0;
+  const hasVo2 = (vo2Summary?.count ?? 0) > 0;
   const hasBpInTarget = data?.bpInTargetPct != null;
 
   // Tile (strip) gates — controlled by the new `tileVisible` flag.
@@ -317,6 +323,7 @@ export default function DashboardPage() {
   const showMoodTile = isTileVisible("mood") && hasMood;
   const showSleepTile = isTileVisible("sleep") && hasSleep;
   const showStepsTile = isTileVisible("steps") && hasSteps;
+  const showVo2Tile = isTileVisible("vo2Max") && hasVo2;
   const showBpInTargetTile = isTileVisible("bpInTarget") && hasBpInTarget;
 
   // Chart (lower row) gates — controlled by the legacy `visible` flag.
@@ -809,6 +816,35 @@ export default function DashboardPage() {
             ),
           });
         }
+        // v1.4.25 W8d — VO2 max trend tile. Self-gates on the
+        // `vo2Max` widget being enabled (Settings → Dashboard) AND
+        // the analytics summary carrying at least one sample. Higher
+        // VO2 max is better, so the directionSentiment is up-good and
+        // an upward 30-day slope renders the green arrow. Unit
+        // matches the canonical DB unit in
+        // src/lib/validations/measurement.ts.
+        if (showVo2Tile) {
+          trendCards.push({
+            id: "vo2Max",
+            order: widgetOrder("vo2Max"),
+            node: (
+              <TrendCard
+                key="vo2Max"
+                label={t("dashboard.vo2Max") ?? "VO₂ max"}
+                latest={vo2Summary?.latest ?? null}
+                unit={t("dashboard.vo2MaxUnit") ?? "mL/(kg·min)"}
+                avg7={vo2Summary?.avg7 ?? null}
+                avg30={vo2Summary?.avg30 ?? null}
+                slope30={vo2Summary?.slope30 ?? null}
+                trend7Delta={summaryToTrend7Delta(vo2Summary)}
+                icon={Gauge}
+                directionSentiment="up-good"
+                compareBaseline={compareBaseline}
+                compareDelta={tileCompareDelta(vo2Summary)}
+              />
+            ),
+          });
+        }
         if (showBpInTargetTile) {
           /* v1.4.22 A2 — feature parity with every other tile.
              Synthesise a slope from the difference between the 7-day

src/components/settings/dashboard-layout-section.tsx

@@ -48,6 +48,8 @@ const WIDGET_LABEL_KEYS: Record<DashboardWidgetId, string> = {
   // for the polished `<InsightsCardPreview>` (top severity-ordered AI
   // recommendations + ring confidence meter + "View all" CTA).
   insightsPreview: "dashboard.insightsPreview",
+  // v1.4.25 W8d — VO2 max secondary-metric tile (opt-in).
+  vo2Max: "dashboard.vo2Max",
 };
 
 export function DashboardLayoutSection({ id }: { id: string }) {

src/lib/dashboard-layout.ts

@@ -34,6 +34,12 @@ export const DASHBOARD_WIDGET_IDS = [
   // a `visible` (chart-row) surface; tileVisible is forced false because
   // there's no tile-strip representation for it.
   "insightsPreview",
+  // v1.4.25 W8d — VO2 max trend tile (opt-in, secondary-metric pattern).
+  // Self-gates on having any VO2_MAX sample; default-invisible so
+  // existing dashboards stay unchanged until the user enables it in
+  // Settings → Dashboard. Only the tile-strip surface; chart row
+  // lands alongside the iOS-app body-composition sub-page in v1.5.
+  "vo2Max",
 ] as const;
 
 export type DashboardWidgetId = (typeof DASHBOARD_WIDGET_IDS)[number];
@@ -217,6 +223,11 @@ export const DEFAULT_DASHBOARD_LAYOUT: DashboardLayout = {
     // so it stays pinned above charts even if the user reorders other
     // widgets; only the boolean visibility flag is consumed.
     { id: "insightsPreview", visible: true, tileVisible: false, order: 14 },
+    // v1.4.25 W8d — VO2 max trend tile. Default-invisible on both
+    // surfaces; opt-in via Settings → Dashboard. Only the tile-strip
+    // representation today (`visible` stays false so the chart-row
+    // gate never fires; the chart card lands in v1.5).
+    { id: "vo2Max", visible: false, tileVisible: false, order: 15 },
   ],
 };