feat: fase 2+3 — expansion masiva multi-perfil + bug fixes + hardening

Fase 2 (expansion):
- Francesca: +6 etapas matematicas (5-10), +7 etapas lectura (3-9), +2 ortografia
- Sebastian: +8 etapas matematicas (4-11), +6 lectura, +3 historia, +3 geografia, +1 banderas
- Nuevas paginas: ortografia, lectura, geografia, matematicas
- ~900 ejercicios nuevos, paridad ~500 por perfil

Fase 3 (bug fixes + hardening):
- Fix: SessionLog auto-create en grade route
- Fix: engine cache (no borrar antes de revisar)
- Fix: FSRS cards actualizadas en flujo curriculum
- Fix: responseMs real (no hardcodeado 3000)
- Fix: options dentro de content en sebastian etapa-1
- Fix: trazo-letra consonantes crash
- Security: execFileSync anti-command-injection en TTS
- DB: 18 cascade deletes + indices + unique constraints
- APIs debug: reset, state, seed
- Docker: espeak-ng + prisma + user/group
- E2E: 23 tests nuevos (curriculum-flow.spec.ts)
- Code review: tailwind colors, middleware dev mode, eslint config

Verificado: tsc exit 0, build exit 0, 61 E2E tests pass

middleware.ts

@@ -19,20 +19,20 @@ export function middleware(request: NextRequest) {
   }
 
   if (isDev) {
-    if (pathname.startsWith("/child") || pathname.startsWith("/parent")) {
-      return NextResponse.next()
-    }
-    const url = request.nextUrl.clone()
-    url.pathname = "/child"
-    return NextResponse.rewrite(url)
+    return NextResponse.next()
   }
 
   if (hostname.includes(CHILD_HOST)) {
-    if (pathname === "/" || pathname.startsWith("/child")) {
+    if (
+      pathname === "/" ||
+      pathname.startsWith("/child") ||
+      pathname.startsWith("/francesca") ||
+      pathname.startsWith("/sebastian")
+    ) {
       return NextResponse.next()
     }
     const url = request.nextUrl.clone()
-    url.pathname = `/child${pathname === "/" ? "" : pathname}`
+    url.pathname = "/"
     return NextResponse.rewrite(url)
   }