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

curriculum/francesca/etapa-3.ts

@@ -0,0 +1,44 @@
+import type { Stage } from '../types'
+
+const restas = [
+  { a: 10, b: 3, res: 7 }, { a: 50, b: 20, res: 30 }, { a: 90, b: 45, res: 45 },
+  { a: 100, b: 35, res: 65 }, { a: 200, b: 75, res: 125 }, { a: 80, b: 23, res: 57 },
+  { a: 120, b: 40, res: 80 }, { a: 55, b: 22, res: 33 }, { a: 75, b: 30, res: 45 },
+  { a: 150, b: 60, res: 90 }, { a: 300, b: 100, res: 200 }, { a: 99, b: 33, res: 66 },
+  { a: 45, b: 12, res: 33 }, { a: 180, b: 50, res: 130 },
+]
+
+const exercises: any[] = []
+for (let i = 0; i < restas.length; i++) {
+  const r = restas[i]
+  const wrong1 = r.res - 10
+  const wrong2 = r.res + 10
+  exercises.push({
+    id: `fra3-resta-${i}`,
+    stage: 3,
+    skillCode: `resta2-${i}`,
+    type: 'eleccion',
+    prerequisites: i === 0 ? ['fra1-suma-9-1'] : [`fra3-resta-${i - 1}`],
+    content: {
+      instruction: `Restá: ${r.a} - ${r.b}`,
+      audioText: `${r.a} menos ${r.b} es ${r.res}`,
+      emoji: '➖',
+      options: [
+        { label: String(r.res), correct: true, id: String(r.res) },
+        { label: String(wrong1 >= 0 ? wrong1 : r.res + 5), correct: false, id: `wrong-${i}-a` },
+        { label: String(wrong2), correct: false, id: `wrong-${i}-b` },
+      ].sort(() => Math.random() - 0.5),
+    },
+    functionalContext: 'Restar números de 2 y 3 dígitos con método Montessori.',
+    errorType: 'inversion-letra',
+  })
+}
+
+const stage: Stage = {
+  id: 3,
+  name: 'Restas de 2-3 dígitos',
+  description: 'Resolver restas de números de 2 y 3 dígitos con material concreto.',
+  exercises,
+}
+
+export default stage