feat(cycle): single-day read endpoint, symptom severity, and a richer log-day sheet

Add `GET /api/cycle/day-logs?date=YYYY-MM-DD` returning the full day-log DTO
(or null) for one tz-anchored day so the web log-day sheet pre-fills instead
of opening blank — a blank re-log no longer nulls untouched or HealthKit-sourced
fields. Delete resolves the row id from the same read.

Persist an optional 1-4 Likert severity per symptom link (migration
0133_v1150_cycle_symptom_severity), carried through the shared symptom-link
writer and surfaced in the day-log DTO.

Sheet now captures the previously missing fields — spotting between periods,
pregnancy/progesterone home-test results, contraceptive kind — plus per-symptom
severity chips, a one-tap end-period boundary, and a Delete action. The wheel
ring marker sits at the 12-o'clock origin again (drop the double rotation), the
cycle view goes two-column on desktop, and the empty ring carries a first-period
call to action. New copy is localized across all six locales; the prediction and
fertility surfaces keep their disclaimers.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/app/api/cycle/day-logs/[id]/route.ts

@@ -139,11 +139,7 @@ export const PATCH = apiHandler(
 
     // Replace symptom links only when `symptoms` was supplied.
     if (body.symptoms !== undefined) {
-      await replaceSymptomLinks(
-        user.id,
-        id,
-        body.symptoms.map((s) => s.key),
-      );
+      await replaceSymptomLinks(user.id, id, body.symptoms);
     }
 
     const row = await prisma.cycleDayLog.findUniqueOrThrow({

src/app/api/cycle/day-logs/route.ts

@@ -26,7 +26,10 @@ import {
 } from "@/lib/api-response";
 import { withIdempotency } from "@/lib/idempotency";
 import { requireCycleEnabled } from "@/lib/cycle/gate";
-import { cycleDayLogInputSchema } from "@/lib/validations/cycle";
+import {
+  cycleDayLogInputSchema,
+  cycleDayLogQuerySchema,
+} from "@/lib/validations/cycle";
 import { upsertCycleDayLog } from "@/lib/cycle/day-log-write";
 import { findOwningCycleId } from "@/lib/cycle/cycle-attribution";
 import { toCycleDayLogDTO, dayLogSymptomInclude } from "@/lib/cycle/dto";
@@ -34,6 +37,40 @@ import { DEFAULT_TIMEZONE } from "@/lib/mood/date-key";
 
 export const POST = apiHandler(withIdempotency<[NextRequest]>(postDayLog));
 
+/**
+ * `GET /api/cycle/day-logs?date=YYYY-MM-DD` — the full `CycleDayLogDTO`
+ * for one tz-anchored day, or `null` when nothing is logged. Lets the
+ * log-day sheet pre-fill (no blank-sheet data loss) and Delete resolve the
+ * row id. Gated + owner-scoped + `deletedAt:null`.
+ */
+export const GET = apiHandler(async (request: NextRequest) => {
+  const { user } = await requireAuth();
+
+  const gate = await requireCycleEnabled(user.id, user.gender);
+  if (!gate.enabled) return gate.response;
+
+  const parsed = cycleDayLogQuerySchema.safeParse({
+    date: new URL(request.url).searchParams.get("date"),
+  });
+  if (!parsed.success) {
+    return returnAllZodIssues(parsed.error, 422, {
+      errorCode: "cycle.day-log.invalid",
+    });
+  }
+
+  const row = await prisma.cycleDayLog.findFirst({
+    where: { userId: user.id, date: parsed.data.date, deletedAt: null },
+    include: dayLogSymptomInclude,
+  });
+
+  annotate({
+    action: { name: "cycle.day-log.read", entity_type: "cycle_day_log" },
+    meta: { found: row !== null },
+  });
+
+  return apiSuccess(row ? toCycleDayLogDTO(row) : null);
+});
+
 async function postDayLog(request: NextRequest): Promise<Response> {
   const { user } = await requireAuth();