feat(insights): blood pressure by time of day

Home monitoring reads morning and evening readings as separate sets, so
the blood pressure page now shows the morning, midday and evening means
side by side over the chart's range, each with its count and pulse, and
the morning-minus-evening difference. A control under them narrows the
chart to one part of the day; the choice lives in `?partOfDay=` so it
survives a reload and a shared link, and the whole day keeps a bare URL.

The split is resolved on the server in the record's own time zone and
published as one response, `GET /api/measurements/blood-pressure/time-of-day`,
so every client renders the same numbers. Morning is 04:00 to 11:59,
midday 12:00 to 17:59, evening 18:00 to 03:59: the guidelines define the
sets by waking and bedtime rather than by the clock, so the windows are
wide, and a reading after midnight is a late evening one. Pairs follow
the blood-pressure series' rule (same source within five minutes); the
pulse is the reading's own. A part shows a mean from three readings on.

`GET /api/measurements` takes `partOfDay` on the blood-pressure and pulse
series read: each local day folds only that part's readings, a day runs
from 04:00, and long ranges fold weekly instead of reading rollups that
cannot tell the hour.

Refs #1331

src/lib/openapi/routes/measurements.ts

@@ -14,6 +14,7 @@ import { z } from "zod/v4";
 import type { ZodOpenApiObject } from "zod-openapi";
 import { updateMeasurementSchema } from "@/lib/validations/measurement";
 import { seriesBatchQuerySchema } from "@/lib/validations/series-batch";
+import { bpTimeOfDayQuerySchema } from "@/lib/validations/bp-time-of-day";
 import { deviceTypeEnum } from "@/lib/validations/source-priority";
 import { sleepStageEntrySchema } from "@/lib/validations/sleep-stage-entry";
 import {
@@ -464,6 +465,10 @@ const listMeasurementsMeta = z
       .string()
       .optional()
       .describe("Set on the aggregate modes — the requested grain."),
+    partOfDay: z
+      .enum(["morning", "midday", "evening"])
+      .optional()
+      .describe("Echoed when the series was narrowed with `partOfDay`."),
     droppedDuplicates: z
       .number()
       .int()
@@ -829,7 +834,113 @@ const seriesBatchResponse = z
       "Batched daily series — one rollup-backed series per requested type.",
   });
 
+const bpPartSummary = z
+  .object({
+    part: z
+      .enum(["morning", "midday", "evening"])
+      .describe("The part of the day."),
+    startHour: z
+      .number()
+      .int()
+      .describe("First local hour of the part (inclusive)."),
+    endHour: z
+      .number()
+      .int()
+      .describe(
+        "Local hour the part ends at (exclusive). Smaller than `startHour` when the part runs past midnight (evening: 18 to 4).",
+      ),
+    readingCount: z
+      .number()
+      .int()
+      .describe("Paired systolic/diastolic readings in this part."),
+    systolic: z
+      .number()
+      .int()
+      .nullable()
+      .describe(
+        "Mean systolic in whole mmHg; null while `readingCount` is below `minReadings`.",
+      ),
+    diastolic: z
+      .number()
+      .int()
+      .nullable()
+      .describe("Mean diastolic in whole mmHg; null on the same floor."),
+    pulseReadingCount: z
+      .number()
+      .int()
+      .describe(
+        "Readings in this part that carried a pulse (same source, within five minutes).",
+      ),
+    pulse: z
+      .number()
+      .int()
+      .nullable()
+      .describe(
+        "Mean pulse in whole bpm; null while `pulseReadingCount` is below `minReadings`.",
+      ),
+  })
+  .meta({ id: "BloodPressurePartOfDay" });
+
+const bpTimeOfDayResponse = z
+  .object({
+    days: z.number().int().describe("The window asked for, in local days."),
+    from: isoDateTime().describe("Window start (ISO-8601)."),
+    to: isoDateTime().describe(
+      "Window end: the last instant of today in the record's time zone.",
+    ),
+    timeZone: z
+      .string()
+      .describe("IANA zone the hours were read in (the record's own)."),
+    minReadings: z
+      .number()
+      .int()
+      .describe("Readings a part needs before its mean is given."),
+    readingCount: z
+      .number()
+      .int()
+      .describe("Paired readings in the window, across the three parts."),
+    parts: z
+      .array(bpPartSummary)
+      .describe("Always three entries: morning, midday, evening, in order."),
+    morningEveningDifference: z
+      .object({
+        systolic: z.number().int(),
+        diastolic: z.number().int(),
+      })
+      .nullable()
+      .describe(
+        "Morning mean minus evening mean, from the two whole-mmHg means given above (so it equals their difference exactly). Null unless both parts reach `minReadings`.",
+      ),
+  })
+  .meta({ id: "BloodPressureTimeOfDay" });
+
 export const measurementPaths: NonNullable<ZodOpenApiObject["paths"]> = {
+  "/api/measurements/blood-pressure/time-of-day": {
+    get: {
+      tags: ["Measurements"],
+      summary: "Blood pressure by part of the day",
+      description:
+        "Morning (04:00 to 11:59), midday (12:00 to 17:59) and evening (18:00 to 03:59) means of the paired blood-pressure readings in the window, read in the record's own time zone, with a count per part and the morning-minus-evening difference. Home monitoring guidance reads morning and evening readings as separate sets; the windows are wide so a waking reading and a late bedtime reading land in the right one. A pair is a systolic with the diastolic of the same source within five minutes, from the source the person's ladder picks for the day (the `bloodPressure` series' rule). Every figure is resolved here; a client renders it as given. Auth via cookie or Bearer.",
+      requestParams: {
+        query: bpTimeOfDayQuerySchema,
+      },
+      responses: {
+        ...recordRefusal(),
+        "200": {
+          description: "Resolved summary.",
+          content: {
+            "application/json": {
+              schema: dataEnvelope(
+                bpTimeOfDayResponse,
+                "GetBloodPressureTimeOfDayResponse",
+              ),
+            },
+          },
+        },
+        ...stdResponses,
+      },
+    },
+  },
   "/api/measurements/series-batch": {
     get: {
       tags: ["Measurements"],