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

lib/curriculum/engine.ts

@@ -1,9 +1,53 @@
 import { prisma } from "@/lib/db"
-import { initCurriculum, getLecturaStages, getNumerosStages, getAllLecturaExercises } from "@/curriculum/index"
-import type { Exercise } from "@/curriculum/types"
+import type { Exercise, Stage } from "@/curriculum/types"
 
 const STAGE_THRESHOLD = 0.8
 
+const PROFILE_CURRICULA: Record<string, Record<string, { folder: string; stages: number[] }>> = {
+  ISABELLA: {
+    lectura: { folder: "lectura", stages: [1, 2, 3, 4, 5, 6, 7, 8, 9] },
+    numeros: { folder: "numeros", stages: [1, 2, 3, 4, 5, 6, 7, 8] },
+  },
+  FRANCESCA: {
+    matematicas: { folder: "francesca", stages: [1, 2, 3, 4] },
+    lecturas: { folder: "francesca-lectura", stages: [1, 2] },
+  },
+  SEBASTIAN: {
+    sumas: { folder: "sebastian", stages: [1, 2, 3] },
+    historia: { folder: "sebastian-historia", stages: [1, 2] },
+    banderas: { folder: "sebastian-banderas", stages: [1] },
+  },
+}
+
+const curriculumCache: Record<string, Record<string, Stage>> = {}
+
+async function getStagesForProfile(
+  profile: string,
+  topic: string,
+): Promise<Record<string, Stage>> {
+  const key = `${profile}-${topic}`
+  // Clear stale cache on every dev call (Next.js hot-reload shares module-level vars)
+  if (curriculumCache[key]) delete curriculumCache[key]
+
+  if (curriculumCache[key]) return curriculumCache[key]
+
+  const config = PROFILE_CURRICULA[profile]?.[topic]
+  if (!config) return {}
+
+  const stages: Record<string, Stage> = {}
+  for (const s of config.stages) {
+    try {
+      const mod = await import(`@/curriculum/${config.folder}/etapa-${s}`)
+      stages[String(s)] = mod.default
+    } catch {
+      // stage not yet implemented
+    }
+  }
+
+  curriculumCache[key] = stages
+  return stages
+}
+
 async function ensureInitialStage(childId: string, topic: string) {
   try {
     const exists = await prisma.curriculumProgress.findFirst({
@@ -30,9 +74,9 @@ export async function getCurrentStage(childId: string, topic: string) {
 
 export async function getNextExercise(
   childId: string,
-  topic: "lectura" | "numeros",
+  topic: string,
+  profile: string = "ISABELLA",
 ): Promise<Exercise | null> {
-  await initCurriculum()
   await ensureInitialStage(childId, topic)
 
   const progress = await prisma.curriculumProgress.findFirst({
@@ -42,8 +86,8 @@ export async function getNextExercise(
 
   if (!progress) return null
 
-  const stages = topic === "lectura" ? getLecturaStages() : getNumerosStages()
-  const stage = stages[progress.stage]
+  const stages = await getStagesForProfile(profile, topic)
+  const stage = stages[String(progress.stage)]
   if (!stage || !stage.exercises.length) return null
 
   const allAttemps = await prisma.skillAttempt.findMany({
@@ -70,7 +114,7 @@ export async function getNextExercise(
       const masteryRatio = mastered.size / stage.exercises.length
       if (masteryRatio >= STAGE_THRESHOLD) {
         await advanceStage(childId, topic, progress.stage)
-        return getNextExercise(childId, topic)
+        return getNextExercise(childId, topic, profile)
       }
     }
     return null