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-1.ts

@@ -0,0 +1,51 @@
+import type { Stage } from '../types'
+
+const sums = Array.from({ length: 15 }, (_, i) => {
+  const a = Math.floor(i / 3) + 1
+  const b = (i % 3) + 1
+  const res = a + b
+  return { a, b, res }
+})
+
+const exercises: any[] = []
+
+for (const s of sums) {
+  const prereqs: string[] = []
+  if (s.a > 1 || s.b > 1) {
+    if (s.b === 1) {
+      prereqs.push(`fra1-suma-${s.a - 1}-1`)
+    } else {
+      prereqs.push(`fra1-suma-1-${s.b - 1}`)
+    }
+  }
+
+  exercises.push({
+    id: `fra1-suma-${s.a}-${s.b}`,
+    stage: 1,
+    skillCode: `suma-${s.a + s.b}`,
+    type: 'sensibilizacion',
+    prerequisites: prereqs,
+    content: {
+      instruction: `Sumá: ${s.a} + ${s.b}`,
+      audioText: `${s.a} más ${s.b} es ${s.res}`,
+      emoji: '🧮',
+      color: '#8CB8A0',
+      options: [
+        { label: String(s.res), correct: true, id: String(s.res) },
+        { label: String(s.res - 1), correct: false, id: String(s.res - 1) },
+        { label: String(s.res + 1), correct: false, id: String(s.res + 1) },
+      ].sort(() => Math.random() - 0.5),
+    },
+    functionalContext: `Sumar ${s.a} + ${s.b} con método Montessori.`,
+    errorType: 'discriminacion-auditiva',
+  })
+}
+
+const stage: Stage = {
+  id: 1,
+  name: 'Sumas de 1 dígito',
+  description: 'Aprender sumas básicas del 1 al 9 con material concreto Montessori.',
+  exercises,
+}
+
+export default stage