feat(targets): 30-day sparkline + Δ-vs-last-month caption per card

The Zielwerte page read as a static reference cheat-sheet — every card
surfaced a current value + range bar but no recent trajectory. Each
target now grows a dependency-free 30-day sparkline beneath the range
bar plus a localised "Δ −2.3 kg vs. last month" caption so the page
reads as a living health log rather than a guideline lookup.

The API computes both fields from a single 60-day query (one round-trip,
not two): `points30d` is the daily-mean series for the last 30 days,
`deltaVsLastMonth` is the signed difference between the current and
prior 30-day averages. Both are null when either window has fewer than
3 readings so cold-start accounts don't see a misleading flat trace
or a "± 0" comparison that's really "no comparison".

BMI piggybacks on the weight series (divided by height²) so the BMI
card's sparkline matches its range bar's y-axis. Derived metrics
(BP-in-target rate, mood stability, medication compliance,
blood-glucose-by-context) keep their previous chrome — the rich
status surface they already render is the right answer there.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/api/insights/targets/route.ts

@@ -56,6 +56,19 @@ interface TargetItem {
   range: { min: number; max: number } | null;
   classification: { category: string; color: string } | null;
   source: string;
+  /**
+   * v1.4.22 C1 — sparkline support on the Zielwerte page. `points30d`
+   * is the last 30 days of values (chronological, oldest → newest) for
+   * the target's primary metric, rounded to one decimal. Derived metrics
+   * (BMI, BP-in-target, mood stability, glucose-by-context) skip the
+   * field when the page already renders a richer status surface.
+   * `deltaVsLastMonth` is the signed difference between the current
+   * 30-day average and the prior 30-day average (current − prior),
+   * null when either window has fewer than 3 points to keep the
+   * comparison honest.
+   */
+  points30d?: number[] | null;
+  deltaVsLastMonth?: number | null;
   details?: {
     medications?: Array<{
       name: string;
@@ -98,17 +111,28 @@ export const GET = apiHandler(async () => {
   ];
 
   const thirtyDaysAgo = new Date(Date.now() - 30 * 24 * 60 * 60 * 1000);
+  // v1.4.22 C1 — second 30-day window (days 31–60) so each target card
+  // can render a "Δ vs. last month" caption alongside its sparkline.
+  // We fetch 60 days in one query to keep the route round-trip count
+  // identical to the previous version.
+  const sixtyDaysAgo = new Date(Date.now() - 60 * 24 * 60 * 60 * 1000);
 
-  // Fetch all measurements in the last 30 days + the latest for each type
-  const recentMeasurements = await prisma.measurement.findMany({
+  // Fetch all measurements in the last 60 days + the latest for each type
+  const windowedMeasurements = await prisma.measurement.findMany({
     where: {
       userId,
       type: { in: types },
-      measuredAt: { gte: thirtyDaysAgo },
+      measuredAt: { gte: sixtyDaysAgo },
     },
     orderBy: { measuredAt: "desc" },
     select: { type: true, value: true, measuredAt: true },
   });
+  const recentMeasurements = windowedMeasurements.filter(
+    (m) => m.measuredAt >= thirtyDaysAgo,
+  );
+  const priorMeasurements = windowedMeasurements.filter(
+    (m) => m.measuredAt < thirtyDaysAgo,
+  );
 
   // Also get the absolute latest measurement per type (even if older than 30 days).
   // Single grouped query replaces the previous N×findFirst loop — DISTINCT ON
@@ -163,6 +187,45 @@ export const GET = apiHandler(async () => {
     return "stable";
   }
 
+  /**
+   * v1.4.22 C1 — sparkline + delta helpers. The sparkline collapses
+   * the last 30 days of values for a measurement type into a daily
+   * mean series (chronological, oldest → newest). The delta is the
+   * signed difference between the current 30-day window's average
+   * and the prior 30-day window's average. Both helpers skip the
+   * computation when there are fewer than 3 points in a window so
+   * the comparison stays honest on cold-start accounts.
+   */
+  function sparklinePoints(type: MeasurementType): number[] | null {
+    const data = recentMeasurements
+      .filter((m) => m.type === type)
+      .sort((a, b) => a.measuredAt.getTime() - b.measuredAt.getTime());
+    if (data.length < 3) return null;
+
+    const byDay = new Map<string, { sum: number; count: number }>();
+    for (const m of data) {
+      const day = m.measuredAt.toISOString().slice(0, 10);
+      const bucket = byDay.get(day) ?? { sum: 0, count: 0 };
+      bucket.sum += m.value;
+      bucket.count += 1;
+      byDay.set(day, bucket);
+    }
+    return Array.from(byDay.values()).map(
+      (b) => Math.round((b.sum / b.count) * 10) / 10,
+    );
+  }
+
+  function deltaVsLastMonth(type: MeasurementType): number | null {
+    const recentOfType = recentMeasurements.filter((m) => m.type === type);
+    const priorOfType = priorMeasurements.filter((m) => m.type === type);
+    if (recentOfType.length < 3 || priorOfType.length < 3) return null;
+    const recentAvg =
+      recentOfType.reduce((s, m) => s + m.value, 0) / recentOfType.length;
+    const priorAvg =
+      priorOfType.reduce((s, m) => s + m.value, 0) / priorOfType.length;
+    return Math.round((recentAvg - priorAvg) * 10) / 10;
+  }
+
   // Build target items
   const targets: TargetItem[] = [];
 
@@ -185,6 +248,8 @@ export const GET = apiHandler(async () => {
     range: weightRange,
     classification: weightClassification,
     source: "WHO BMI",
+    points30d: sparklinePoints("WEIGHT"),
+    deltaVsLastMonth: deltaVsLastMonth("WEIGHT"),
   });
 
   // 2. Blood Pressure (sys/dia combined)
@@ -210,6 +275,8 @@ export const GET = apiHandler(async () => {
     range: bpRange ? { min: bpRange.sysLow, max: bpRange.sysHigh } : null,
     classification: bpClassification,
     source: "ESH 2023",
+    points30d: sparklinePoints("BLOOD_PRESSURE_SYS"),
+    deltaVsLastMonth: deltaVsLastMonth("BLOOD_PRESSURE_SYS"),
     // Extra fields for diastolic
   } as TargetItem);
 
@@ -276,6 +343,8 @@ export const GET = apiHandler(async () => {
     range: { min: pulseTarget.greenMin, max: pulseTarget.greenMax },
     classification: pulseClassification,
     source: pulseTarget.source,
+    points30d: sparklinePoints("PULSE"),
+    deltaVsLastMonth: deltaVsLastMonth("PULSE"),
   });
 
   // 4. Sleep Duration
@@ -295,6 +364,8 @@ export const GET = apiHandler(async () => {
     range: sleepRange,
     classification: sleepClassification,
     source: "AASM/SRS",
+    points30d: sparklinePoints("SLEEP_DURATION"),
+    deltaVsLastMonth: deltaVsLastMonth("SLEEP_DURATION"),
   });
 
   // 5. BMI (derived from weight + height)
@@ -318,6 +389,19 @@ export const GET = apiHandler(async () => {
       bmiClassification = { category: cls.category, color: cls.color };
     }
 
+    // BMI sparkline / delta derive from the weight series \u2014 divide each
+    // point by height\u00B2 so the y-axis matches the BMI range bar above.
+    const weightPoints = sparklinePoints("WEIGHT");
+    const bmiPoints =
+      weightPoints != null
+        ? weightPoints.map((v) => Math.round((v / heightSq) * 10) / 10)
+        : null;
+    const weightDelta = deltaVsLastMonth("WEIGHT");
+    const bmiDelta =
+      weightDelta != null
+        ? Math.round((weightDelta / heightSq) * 10) / 10
+        : null;
+
     targets.push({
       type: "BMI",
       label: "BMI",
@@ -328,6 +412,8 @@ export const GET = apiHandler(async () => {
       range: { min: 18.5, max: 24.9 },
       classification: bmiClassification,
       source: "WHO",
+      points30d: bmiPoints,
+      deltaVsLastMonth: bmiDelta,
     });
   }
 
@@ -353,6 +439,8 @@ export const GET = apiHandler(async () => {
     range: bodyFatRange,
     classification: bodyFatClassification,
     source: "ACE",
+    points30d: sparklinePoints("BODY_FAT"),
+    deltaVsLastMonth: deltaVsLastMonth("BODY_FAT"),
   });
 
   // 7. Activity Steps
@@ -371,6 +459,8 @@ export const GET = apiHandler(async () => {
     unit: "steps",
     range: stepsRange,
     classification: stepsClassification,
+    points30d: sparklinePoints("ACTIVITY_STEPS"),
+    deltaVsLastMonth: deltaVsLastMonth("ACTIVITY_STEPS"),
     // WHO publishes activity *time* (150–300 min/wk moderate),
     // not a step quota. The closest peer-reviewed dose-response
     // for the 8 000–15 000 band is Saint-Maurice JAMA 2020. The