feat: fase 5 — botones volver, seguridad APIs, infraestructura

- Botón 'Volver' en todas las sesiones de ejercicios (ExerciseSession)
- Botón 'Cambiar perfil' en las 3 home pages (Isabella/Francesca/Sebastián)
- Páginas inline de Isabella migradas a ExerciseSession (elimina código duplicado)
- APIs con try/catch: curriculum/next, dashboard/summary, fsrs/next, children
- Validación childId en curriculum/next (404 si no existe)
- /api/health endpoint para Docker healthcheck
- .env.example, .dockerignore, README.md creados
- docker-compose.yml con healthcheck en app service
- Test E2E: health endpoint + childId validation
- 62/62 tests pasan, TS exit 0

app/api/fsrs/next/route.ts

@@ -3,33 +3,38 @@ import { prisma } from "@/lib/db"
 import { buildFsrsCard, getRetrievability } from "@/lib/fsrs"
 
 export async function GET(request: NextRequest) {
-  const childId = request.nextUrl.searchParams.get("childId")
-  if (!childId) {
-    return NextResponse.json({ error: "childId required" }, { status: 400 })
-  }
+  try {
+    const childId = request.nextUrl.searchParams.get("childId")
+    if (!childId) {
+      return NextResponse.json({ error: "childId required" }, { status: 400 })
+    }
 
-  const dueCard = await prisma.fsrsCard.findFirst({
-    where: {
-      childId,
-      dueAt: { lte: new Date() },
-    },
-    orderBy: { dueAt: "asc" },
-  })
-
-  if (dueCard) {
-    const card = buildFsrsCard({
-      stability: dueCard.stability,
-      difficulty: dueCard.difficulty,
-      reps: dueCard.reps,
-      lapses: dueCard.lapses,
-      due: dueCard.dueAt,
+    const dueCard = await prisma.fsrsCard.findFirst({
+      where: {
+        childId,
+        dueAt: { lte: new Date() },
+      },
+      orderBy: { dueAt: "asc" },
     })
-    return NextResponse.json({
-      ...dueCard,
-      cardId: dueCard.id,
-      retrievability: getRetrievability(card),
-    })
-  }
 
-  return NextResponse.json({ skillCode: null })
+    if (dueCard) {
+      const card = buildFsrsCard({
+        stability: dueCard.stability,
+        difficulty: dueCard.difficulty,
+        reps: dueCard.reps,
+        lapses: dueCard.lapses,
+        due: dueCard.dueAt,
+      })
+      return NextResponse.json({
+        ...dueCard,
+        cardId: dueCard.id,
+        retrievability: getRetrievability(card),
+      })
+    }
+
+    return NextResponse.json({ skillCode: null })
+  } catch (error) {
+    console.error("[fsrs/next] error:", error)
+    return NextResponse.json({ error: "Internal error" }, { status: 500 })
+  }
 }