fix(vaccinations): keep the booster mint inside the sections the grant opens

`POST /api/vaccinations/{id}/booster` is declared `("write", "profile")`, and
that is right for the act — filing the Impfpass and arming the booster it
suggests are one thing to the person doing them. The row it writes is not: a
`MeasurementReminder` belongs to the measurements section, every direct route
over the model declares it there, and creating one needs MANAGE. So a WRITE
grant scoped to the health background alone produced a reminder on the owner's
checkup list that the delegate could neither read nor change through the
section that owns it.

The seam is fenced the way the visits service fences a checkup closure, with
one difference stated at the call site: this refuses rather than skips. There
the closure is one effect of a larger save and reporting it as not done keeps
the save honest; here the reminder is the whole request, and a 201 over a row
that was never written would tell the person their booster is planned while
nothing rings. The prompt that raises the call asks the same question client-
side, so a delegate outside the section is not offered it in the first place;
the dose itself still logs either way.

`vaccination-booster-scoped-delegate.test.ts` drives the owner, a delegate
holding both sections, a profile-only delegate and a whole-record one. The
scoped-refusal leg fails against the previous handler, which answered 201 and
left the row.

tests/integration/vaccination-booster-scoped-delegate.test.ts

@@ -0,0 +1,166 @@
+/**
+ * `POST /api/vaccinations/{id}/booster` crosses a section boundary, and the
+ * grant has to be on both sides of it.
+ *
+ * The operation is declared `("write", "profile")`, which is right for the act
+ * — filing the Impfpass and arming the booster it suggests are one thing to
+ * the person doing them. The ROW it mints is not: a `MeasurementReminder`
+ * belongs to the measurements section, every direct route over that model says
+ * so, and creating one there needs MANAGE. So a grant opening the health
+ * background alone would otherwise produce a reminder on the owner's checkup
+ * list that the delegate can neither read nor change through the section that
+ * owns it.
+ *
+ * Refused rather than silently skipped: the reminder is the whole request, and
+ * a 201 over a row that was never written would tell the person their booster
+ * is planned while nothing rings.
+ */
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+process.env.ENCRYPTION_KEY ??=
+  "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef";
+
+import { NextRequest } from "next/server";
+
+import type { ShareDomain } from "@/lib/sharing/scope";
+
+import { cookieJar, headerJar } from "./mock-next-headers";
+import { getPrismaClient, truncateAllTables, switchSessionTo } from "./setup";
+
+vi.mock("next/headers", async () => {
+  const { cookieJar, headerJar } = await import("./mock-next-headers");
+  return {
+    headers: vi.fn(async () => ({
+      get: (name: string) => headerJar.get(name.toLowerCase()) ?? null,
+    })),
+    cookies: vi.fn(async () => ({
+      get: (name: string) => {
+        const value = cookieJar.get(name);
+        return value ? { name, value } : undefined;
+      },
+      set: (name: string, value: string) => cookieJar.set(name, value),
+      delete: (name: string) => cookieJar.delete(name),
+    })),
+  };
+});
+
+vi.mock("@/lib/db-compat", () => ({
+  ensureDbCompatibility: vi.fn().mockResolvedValue(undefined),
+}));
+
+const OWNER_ID = "booster-scope-owner";
+const DELEGATE_ID = "booster-scope-delegate";
+
+/** A catalogue antigen that carries a booster interval. */
+const ANTIGEN = "tetanus";
+
+let doseId: string;
+
+async function seedRecords() {
+  const prisma = getPrismaClient();
+  for (const [id, name] of [
+    [OWNER_ID, "owner"],
+    [DELEGATE_ID, "delegate"],
+  ] as const) {
+    await prisma.user.create({
+      data: {
+        id,
+        username: `booster-scope-${name}`,
+        email: `booster-scope-${name}@example.test`,
+        timezone: "UTC",
+      },
+    });
+  }
+  const dose = await prisma.vaccinationRecord.create({
+    data: {
+      userId: OWNER_ID,
+      occurredAt: new Date("2026-03-01T00:00:00.000Z"),
+      antigenSlug: ANTIGEN,
+    },
+  });
+  doseId = dose.id;
+}
+
+async function signIn(userId: string) {
+  const session = await getPrismaClient().session.create({
+    data: { userId, expiresAt: new Date(Date.now() + 24 * 60 * 60 * 1000) },
+  });
+  cookieJar.set("healthlog_session", session.id);
+  return session;
+}
+
+async function switchInto(
+  access: "WRITE" | "MANAGE",
+  scope: ShareDomain[] | null,
+) {
+  const { inviteGrant, acceptGrant } = await import("@/lib/sharing/grants");
+  const invited = await inviteGrant({
+    grantorId: OWNER_ID,
+    granteeId: DELEGATE_ID,
+    access,
+    scope,
+  });
+  await acceptGrant({ grantId: invited.id, granteeId: DELEGATE_ID });
+  const session = await signIn(DELEGATE_ID);
+  await switchSessionTo(session.id, OWNER_ID);
+}
+
+async function planBooster(): Promise<Response> {
+  const { POST } = await import("@/app/api/vaccinations/[id]/booster/route");
+  return POST(
+    new NextRequest(`http://localhost/api/vaccinations/${doseId}/booster`, {
+      method: "POST",
+      headers: { "content-type": "application/json" },
+      body: JSON.stringify({ intervalMonths: 120, label: "Tetanus booster" }),
+    }),
+    { params: Promise.resolve({ id: doseId }) },
+  );
+}
+
+beforeEach(async () => {
+  await truncateAllTables(getPrismaClient());
+  cookieJar.clear();
+  headerJar.clear();
+  await seedRecords();
+});
+
+describe("planning a booster asks for the section the reminder lives in", () => {
+  it("mints for the owner", async () => {
+    await signIn(OWNER_ID);
+    expect((await planBooster()).status).toBe(201);
+    expect(
+      await getPrismaClient().measurementReminder.count({
+        where: { userId: OWNER_ID },
+      }),
+    ).toBe(1);
+  });
+
+  it("mints for a delegate holding both sections", async () => {
+    await switchInto("WRITE", ["profile", "measurements"]);
+    expect((await planBooster()).status).toBe(201);
+    expect(
+      await getPrismaClient().measurementReminder.count({
+        where: { userId: OWNER_ID },
+      }),
+    ).toBe(1);
+  });
+
+  it("refuses a profile-only delegate and writes no reminder", async () => {
+    await switchInto("WRITE", ["profile"]);
+    const response = await planBooster();
+    expect(response.status).toBe(403);
+    const body = (await response.json()) as { meta?: { errorCode?: string } };
+    expect(body.meta?.errorCode).toBe("vaccination.booster-out-of-scope");
+    expect(
+      await getPrismaClient().measurementReminder.count({
+        where: { userId: OWNER_ID },
+      }),
+      "no reminder was left on the owner's checkup list",
+    ).toBe(0);
+  });
+
+  it("mints for a whole-record delegate", async () => {
+    await switchInto("MANAGE", null);
+    expect((await planBooster()).status).toBe(201);
+  });
+});