fix(nutrients): count each day once and anchor the overview window on user tz

GET /api/nutrients had two correctness bugs:

- `daysWithData` incremented on every row whose day differed from the
  PINNED latest-day field, so a second source's row on an already-seen
  older day (water logged via both Apple Health and a manual entry on
  the same day) opened a phantom second "day". Track a per-nutrient
  set of distinct day keys instead.
- The window floor used a UTC day key against a local-timezone `day`
  column, off by up to a day at the edge for non-UTC users. Anchor on
  the caller's own local "today" instead, mirroring the sibling
  `GET /api/nutrients/daily` route.

src/app/api/nutrients/__tests__/route.test.ts

@@ -132,6 +132,32 @@ describe("GET /api/nutrients", () => {
     ]);
   });
 
+  it("counts a multi-source day once (DATAINT M3 regression)", async () => {
+    // v1.29 migration 0249 lets a day carry one row per source. A non-latest
+    // day logged via both APPLE_HEALTH and MANUAL must still count as ONE
+    // day, not two.
+    vi.mocked(prisma.nutrientIntakeDay.findMany).mockResolvedValue([
+      { nutrient: "water", unit: "ml", day: "2026-07-13", amount: 900 },
+      { nutrient: "water", unit: "ml", day: "2026-07-12", amount: 600 },
+      { nutrient: "water", unit: "ml", day: "2026-07-12", amount: 400 },
+      { nutrient: "water", unit: "ml", day: "2026-07-11", amount: 500 },
+    ] as never);
+
+    const res = await GET(getReq("?days=7"));
+    const body = (await res.json()) as OverviewResponse;
+    const water = body.data.nutrients.find((n) => n.nutrient === "water");
+    expect(water).toEqual({
+      nutrient: "water",
+      unit: "ml",
+      latestDay: "2026-07-13",
+      latestAmount: 900,
+      // Three distinct days (13th, 12th, 11th) — the buggy version counted
+      // four, since the 12th's second source row didn't match the pinned
+      // `latestDay` (the 13th) and opened a phantom extra day.
+      daysWithData: 3,
+    });
+  });
+
   it("scopes the query to the authenticated user and the window floor", async () => {
     await GET(getReq("?days=14"));
     expect(prisma.nutrientIntakeDay.findMany).toHaveBeenCalledWith(

src/app/api/nutrients/route.ts

@@ -17,6 +17,7 @@ import { annotate } from "@/lib/logging/context";
 import { requireModuleEnabled } from "@/lib/modules/gate";
 import { NUTRIENT_CODES, isNutrientCode } from "@/lib/nutrients/catalog";
 import { nutrientOverviewQuerySchema } from "@/lib/validations/nutrients";
+import { DEFAULT_TIMEZONE, shiftDateKey, userDayKey } from "@/lib/tz/format";
 
 export const dynamic = "force-dynamic";
 
@@ -36,12 +37,14 @@ export const GET = apiHandler(async (request: NextRequest) => {
   }
   const { days } = parsed.data;
 
-  // Window floor as a UTC day key. The stored `day` is a local-timezone
-  // key, so the UTC floor is off by at most one calendar day at the
-  // window edge — fine for a "last N days" summary card.
-  const since = new Date(Date.now() - (days - 1) * 24 * 60 * 60 * 1000)
-    .toISOString()
-    .slice(0, 10);
+  // v1.30 (DATAINT L4) — window floor anchored on the caller's own local
+  // "today" (`User.timezone`), mirroring the sibling `GET
+  // /api/nutrients/daily` route. The stored `day` is a local-timezone key,
+  // so a UTC floor was off by up to a calendar day at the window edge for
+  // any non-UTC user.
+  const userTz = user.timezone || DEFAULT_TIMEZONE;
+  const todayKey = userDayKey(new Date(), userTz);
+  const since = shiftDateKey(todayKey, -(days - 1));
 
   const rows = await prisma.nutrientIntakeDay.findMany({
     where: { userId: user.id, day: { gte: since } },
@@ -50,14 +53,26 @@ export const GET = apiHandler(async (request: NextRequest) => {
   });
 
   // v1.29 — `source` joined the PK (migration 0249): a day can now carry
-  // an APPLE_HEALTH row AND a MANUAL row, so the fold sums amounts
-  // WITHIN (nutrient, day) before folding across days. Rows arrive
-  // day-DESC inside each nutrient, so the first DAY seen per code is
-  // the latest; a second row for that same day (the other source) adds
-  // to the running total instead of opening a new "day".
+  // an APPLE_HEALTH row AND a MANUAL row. Rows arrive day-DESC inside each
+  // nutrient, so the first DAY seen per code is the latest; a second row
+  // for that same day (the other source) adds to the running total instead
+  // of opening a new "day".
+  //
+  // v1.30 (DATAINT M3) — `daysWithData` used to increment on every row
+  // whose `day` differed from the PINNED `latestDay` field, so a second
+  // source's row on an already-counted OLDER day (e.g. water logged via
+  // both APPLE_HEALTH and MANUAL on the same non-latest day) opened a
+  // second "day" for that same calendar date. `daysSeen` is a per-nutrient
+  // set of distinct day keys — every row adds to it, so a repeated day
+  // (any number of source rows) is counted exactly once.
   const byCode = new Map<
     string,
-    { unit: string; latestDay: string; latestAmount: number; days: number }
+    {
+      unit: string;
+      latestDay: string;
+      latestAmount: number;
+      daysSeen: Set<string>;
+    }
   >();
   for (const row of rows) {
     const existing = byCode.get(row.nutrient);
@@ -66,12 +81,13 @@ export const GET = apiHandler(async (request: NextRequest) => {
         unit: row.unit,
         latestDay: row.day,
         latestAmount: row.amount,
-        days: 1,
+        daysSeen: new Set([row.day]),
       });
-    } else if (row.day === existing.latestDay) {
+      continue;
+    }
+    existing.daysSeen.add(row.day);
+    if (row.day === existing.latestDay) {
       existing.latestAmount += row.amount;
-    } else {
-      existing.days += 1;
     }
   }
 
@@ -86,7 +102,7 @@ export const GET = apiHandler(async (request: NextRequest) => {
       unit: summary.unit,
       latestDay: summary.latestDay,
       latestAmount: summary.latestAmount,
-      daysWithData: summary.days,
+      daysWithData: summary.daysSeen.size,
     };
   });