feat(charts): weight chart accepts vertical injection-day markers

Adds an optional `verticalMarkers` prop to `<HealthChart>` so the
v1.4.25 GLP-1 dashboard tile + the Insights /medikamente sub-page can
paint dashed vertical reference lines at each recorded injection day.
Each marker = `{ date: 'YYYY-MM-DD', label?, color? }`. Defaults to
the strip-tile green (`#50fa7b`) so a row of markers reads as
"injection cadence" at a glance; callers can override per marker.

Rendering:
  - Recharts `<ReferenceLine>` with `strokeDasharray='3 3'`,
    `strokeOpacity=0.55`, no label by default (inline labels would
    crowd a once-weekly cadence over a 90-day window).
  - A small filled `<ReferenceDot>` (r=3) at the y-axis minimum so
    the markers also read along the x-axis baseline.
  - Off-window markers silently drop via `ifOverflow='discard'`,
    matching the existing storyboard-annotation contract.

The marker math is factored into a pure helper
`resolveVerticalMarkerPositions` so the unit suite can pin behaviour
without mounting Recharts. Day-keys are matched by EXACT string
comparison against `chartData[i].date` (no ±7-day snap like the
storyboard annotations) — drawing a marker on a day the chart has no
data point reads as a rendering bug rather than as orientation.

Tests pin: empty input, undefined input, single in-window match,
multi-marker order, caller-supplied color/label overrides, off-window
drop, sparse weekly-bucket exact-day matching.

src/components/charts/__tests__/health-chart-vertical-markers.test.ts

@@ -0,0 +1,112 @@
+import { describe, it, expect } from "vitest";
+import { resolveVerticalMarkerPositions } from "../health-chart";
+
+/**
+ * v1.4.25 W6 — GLP-1 injection-day vertical-marker pinning.
+ *
+ * The helper maps incoming `{date, label?, color?}[]` markers onto the
+ * bucketed chart series, returning the pointIndex of every match plus
+ * the marker's color/label so the chart paints exactly one
+ * `<ReferenceLine>` per matched bucket. Differs from the storyboard
+ * `resolveAnnotationPositions` helper in two ways: it does an EXACT
+ * day-key match (no ±7-day snap, no truncation), and it defaults the
+ * color to the strip-tile green when omitted.
+ *
+ * Pure helper — the suite pins behaviour without mounting Recharts.
+ */
+
+describe("resolveVerticalMarkerPositions", () => {
+  const dailyChartData = Array.from({ length: 10 }, (_, i) => ({
+    date: `2026-04-${String(15 + i).padStart(2, "0")}`,
+  }));
+
+  it("returns empty when markers is undefined", () => {
+    expect(resolveVerticalMarkerPositions(undefined, dailyChartData)).toEqual(
+      [],
+    );
+  });
+
+  it("returns empty when markers is an empty array", () => {
+    expect(resolveVerticalMarkerPositions([], dailyChartData)).toEqual([]);
+  });
+
+  it("returns empty when chartData is undefined or empty", () => {
+    expect(
+      resolveVerticalMarkerPositions(
+        [{ date: "2026-04-15" }],
+        undefined,
+      ),
+    ).toEqual([]);
+    expect(resolveVerticalMarkerPositions([{ date: "2026-04-15" }], [])).toEqual(
+      [],
+    );
+  });
+
+  it("pins a single in-window marker to its exact day-key", () => {
+    const positions = resolveVerticalMarkerPositions(
+      [{ date: "2026-04-15" }],
+      dailyChartData,
+    );
+    expect(positions).toHaveLength(1);
+    expect(positions[0].pointIndex).toBe(0);
+    expect(positions[0].color).toBe("#50fa7b");
+    expect(positions[0].label).toBeUndefined();
+  });
+
+  it("pins multiple markers in input order with the correct pointIndex", () => {
+    const positions = resolveVerticalMarkerPositions(
+      [
+        { date: "2026-04-15" },
+        { date: "2026-04-22" },
+        { date: "2026-04-19" },
+      ],
+      dailyChartData,
+    );
+    expect(positions.map((p) => p.pointIndex)).toEqual([0, 7, 4]);
+  });
+
+  it("respects caller-supplied color + label overrides", () => {
+    const positions = resolveVerticalMarkerPositions(
+      [
+        { date: "2026-04-17", label: "Mounjaro 7.5", color: "#ff79c6" },
+        { date: "2026-04-19" },
+      ],
+      dailyChartData,
+    );
+    expect(positions[0].color).toBe("#ff79c6");
+    expect(positions[0].label).toBe("Mounjaro 7.5");
+    // Default color preserved for the second marker.
+    expect(positions[1].color).toBe("#50fa7b");
+    expect(positions[1].label).toBeUndefined();
+  });
+
+  it("drops markers whose date does not match any visible day-key", () => {
+    const positions = resolveVerticalMarkerPositions(
+      [
+        { date: "2026-04-15" }, // exact match — index 0
+        { date: "2026-03-01" }, // off-window
+        { date: "2026-05-15" }, // off-window
+        { date: "2026-04-24" }, // off-window (visible ends at 2026-04-24? series is 15..24)
+      ],
+      dailyChartData,
+    );
+    // Series is 2026-04-15 .. 2026-04-24. 2026-04-24 is the last entry.
+    expect(positions.map((p) => p.pointIndex)).toEqual([0, 9]);
+  });
+
+  it("handles a sparse weekly-bucket series with exact-day matching only", () => {
+    // Weekly buckets — only the date keys that fall on a bucket day land.
+    const weeklyChartData = ["2026-04-15", "2026-04-22", "2026-04-29"].map(
+      (date) => ({ date }),
+    );
+    const positions = resolveVerticalMarkerPositions(
+      [
+        { date: "2026-04-22" }, // exact bucket day → matches
+        { date: "2026-04-23" }, // between buckets → drops (no ±7 snap)
+      ],
+      weeklyChartData,
+    );
+    expect(positions).toHaveLength(1);
+    expect(positions[0].pointIndex).toBe(1);
+  });
+});

src/components/charts/health-chart.tsx

@@ -13,6 +13,7 @@ import {
   Legend,
   ReferenceLine,
   ReferenceArea,
+  ReferenceDot,
 } from "recharts";
 import { Loader2 } from "lucide-react";
 import { useState, useMemo } from "react";
@@ -138,6 +139,28 @@ interface HealthChartProps {
    * that needs the same behaviour).
    */
   annotations?: Array<{ date: string; label: string; color: string }>;
+  /**
+   * v1.4.25 W6 — vertical injection-day markers.
+   *
+   * Each entry pins a thin dashed vertical reference line on the chart
+   * at the data point whose Berlin/user-tz day-key matches `date`
+   * (`YYYY-MM-DD`). Designed for the GLP-1 dashboard tile + the
+   * Insights /medikamente sub-page so users can see "I injected on
+   * these days; here's how my weight responded". Differs from
+   * `annotations` in three ways:
+   *   1. No text label by default — these markers represent events
+   *      the user already saw the chart-line shape for; an inline
+   *      label per marker would crowd the canvas.
+   *   2. A small filled dot sits at the x-axis intersection (mood-
+   *      chart style emoji-on-axis pattern repurposed) so a row of
+   *      green dots reads as "injection cadence" at a glance.
+   *   3. Default green (`#50fa7b`) to match the strip-tile palette
+   *      for active medications; callers can override per marker.
+   *
+   * Off-window markers silently drop via `ifOverflow="discard"`,
+   * matching the existing annotations contract.
+   */
+  verticalMarkers?: Array<{ date: string; label?: string; color?: string }>;
   /**
    * v1.4.25 W7b — per-user display timezone. When passed (mount sites
    * thread `useAuth().user?.timezone`), x-axis tick labels and the
@@ -291,6 +314,55 @@ export interface ResolvedAnnotation {
   truncatedLabel: string;
 }
 
+/**
+ * v1.4.25 W6 — pure helper for the GLP-1 injection-day vertical
+ * markers. Exported so the unit suite can pin behaviour without
+ * spinning Recharts. The shape mirrors `resolveAnnotationPositions`
+ * minus the truncated-label slot.
+ *
+ * `chartData[i].date` is the `YYYY-MM-DD` day-key the chart already
+ * computed when bucketing measurements; we match by exact key so a
+ * marker only lands on a day the chart actually has a data point for.
+ * This is intentional — drawing a vertical line through a gap in the
+ * x-axis paints a hanging line with no data context, which reads as a
+ * rendering bug not as orientation.
+ *
+ * Off-window markers silently drop (the chart's `<ReferenceLine>` also
+ * uses `ifOverflow="discard"` as a belt-and-braces guard).
+ */
+export interface ResolvedVerticalMarker {
+  pointIndex: number;
+  color: string;
+  label: string | undefined;
+}
+
+export function resolveVerticalMarkerPositions(
+  markers:
+    | Array<{ date: string; label?: string; color?: string }>
+    | undefined,
+  chartData: Array<{ date: string }> | undefined,
+): ResolvedVerticalMarker[] {
+  if (!markers || !chartData || chartData.length === 0) return [];
+  const indexByDate = new Map<string, number>();
+  for (const [i, point] of chartData.entries()) {
+    // Last-write-wins — multiple bucket-aggregated points should never
+    // share the same day key, but defensively keep the latest if they
+    // do.
+    indexByDate.set(point.date, i);
+  }
+  const out: ResolvedVerticalMarker[] = [];
+  for (const marker of markers) {
+    const idx = indexByDate.get(marker.date);
+    if (idx === undefined) continue;
+    out.push({
+      pointIndex: idx,
+      color: marker.color ?? "#50fa7b",
+      label: marker.label,
+    });
+  }
+  return out;
+}
+
 export function resolveAnnotationPositions(
   annotations:
     | Array<{ date: string; label: string; color: string }>
@@ -383,6 +455,7 @@ export function HealthChart({
   compareBaseline = "none",
   chartKey,
   annotations,
+  verticalMarkers,
   userTimezone = "Europe/Berlin",
 }: HealthChartProps) {
   const { isAuthenticated, user } = useAuth();
@@ -954,6 +1027,16 @@ export function HealthChart({
     chartData,
   );
 
+  // v1.4.25 W6 — GLP-1 injection-day vertical markers. Pure-helper
+  // pattern lets the chart-tests pin the marker resolution without
+  // mounting Recharts. Off-window markers silently drop here so the
+  // <ReferenceLine> below never paints a line for an out-of-range
+  // day.
+  const verticalMarkerPositions = resolveVerticalMarkerPositions(
+    verticalMarkers,
+    chartData,
+  );
+
   const showContextDetails = showMA || showTrend || showBands;
   const animationsEnabled = !prefersReducedMotion();
 
@@ -1238,6 +1321,47 @@ export function HealthChart({
                     }}
                   />
                 ))}
+                {/* v1.4.25 W6 — GLP-1 injection-day vertical markers.
+                    Thin dashed line + a small filled dot at the x-axis
+                    intersection so a row of markers reads as "injection
+                    cadence" without crowding the canvas. Optional label
+                    rendered only when the caller passed one; the
+                    dashboard tile leaves it undefined (the date is
+                    redundant — the chart's x-axis already shows it). */}
+                {verticalMarkerPositions.map((marker, i) => (
+                  <ReferenceLine
+                    key={`vmarker-${i}-${marker.pointIndex}`}
+                    x={marker.pointIndex}
+                    stroke={marker.color}
+                    strokeDasharray="3 3"
+                    strokeWidth={1.1}
+                    strokeOpacity={0.55}
+                    ifOverflow="discard"
+                    label={
+                      marker.label
+                        ? {
+                            value: marker.label,
+                            position: "insideTopRight",
+                            fill: marker.color,
+                            fontSize: 10,
+                            fontWeight: 500,
+                          }
+                        : undefined
+                    }
+                  />
+                ))}
+                {yDomain &&
+                  verticalMarkerPositions.map((marker, i) => (
+                    <ReferenceDot
+                      key={`vmarker-dot-${i}-${marker.pointIndex}`}
+                      x={marker.pointIndex}
+                      y={yDomain[0]}
+                      r={3}
+                      fill={marker.color}
+                      stroke="none"
+                      ifOverflow="discard"
+                    />
+                  ))}
                 {/* v1.4.18 — personal-baseline reference line is now
                     opt-in via the Trend toggle. the maintainer rejected the
                     always-on dashed mean line; it now only paints when