feat: multi-profile system with Francesca and Sebastian curricula

- Add Profile enum (ISABELLA, FRANCESCA, SEBASTIAN) to Child model
- Add ?profile= query param override to /api/curriculum/next
- Pass profile prop from profile-specific pages to ExerciseSession
- Fix curriculum import paths (engine uses @/curriculum/ alias)
- Clear stale curriculumCache on dev reload
- Fix self-referential prerequisites in Francesca etapa-1
- Fix prerequisite chains in Francesca etapa-2,3,4 and Sebastian etapa-2,3
- Add Francesca curriculum: 2-3 digit sums, subtractions, multiplications, short readings
- Add Sebastian curriculum: 2-3 digit sums, interactive exercises, Argentine history, flags
- All 44 E2E tests pass, TypeScript compiles cleanly

app/api/curriculum/next/route.ts

@@ -1,13 +1,20 @@
 import { NextRequest, NextResponse } from "next/server"
+import { prisma } from "@/lib/db"
 import { getNextExercise } from "@/lib/curriculum/engine"
 
 export async function GET(request: NextRequest) {
   const childId = request.nextUrl.searchParams.get("childId")
-  const topic = (request.nextUrl.searchParams.get("topic") || "lectura") as "lectura" | "numeros"
+  const topic = request.nextUrl.searchParams.get("topic") || "lectura"
   if (!childId) {
     return NextResponse.json({ error: "childId required" }, { status: 400 })
   }
 
-  const exercise = await getNextExercise(childId, topic)
+  const child = await prisma.child.findUnique({
+    where: { id: childId },
+    select: { profile: true },
+  })
+
+  const profile = (request.nextUrl.searchParams.get("profile") || child?.profile || "ISABELLA").toUpperCase()
+  const exercise = await getNextExercise(childId, topic, profile)
   return NextResponse.json(exercise || { id: null, done: true })
 }