feat: doctor visit log, schedule prediction, chart PDF, natural digest

- Doctor notes: add doctorName, reason, prescriptions, nextAppointmentAt fields (schema + API + UI)
- Dashboard: baby schedule prediction widget (avg nap/bedtime/first-feed over 14 days)
- Growth PDF: embed weight chart as image (SVG→Canvas capture) before data table
- Weekly digest: natural language push notification instead of bullet stats

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

prisma/migrations/20260615203958_enhance_doctor_note/migration.sql

@@ -0,0 +1,5 @@
+-- AlterTable
+ALTER TABLE "DoctorNote" ADD COLUMN     "doctorName" TEXT,
+ADD COLUMN     "nextAppointmentAt" TIMESTAMP(3),
+ADD COLUMN     "prescriptions" TEXT,
+ADD COLUMN     "reason" TEXT;

prisma/schema.prisma

@@ -184,14 +184,18 @@ model GrowthLog {
 }
 
 model DoctorNote {
-  id        String   @id @default(cuid())
-  babyId    String
-  baby      Baby     @relation(fields: [babyId], references: [id], onDelete: Cascade)
-  userId    String
-  user      User     @relation(fields: [userId], references: [id])
-  content   String
-  date      DateTime @default(now())
-  createdAt DateTime @default(now())
+  id                String    @id @default(cuid())
+  babyId            String
+  baby              Baby      @relation(fields: [babyId], references: [id], onDelete: Cascade)
+  userId            String
+  user              User      @relation(fields: [userId], references: [id])
+  content           String
+  doctorName        String?
+  reason            String?
+  prescriptions     String?
+  nextAppointmentAt DateTime?
+  date              DateTime  @default(now())
+  createdAt         DateTime  @default(now())
 }
 
 model JournalNote {