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

eslint.config.mjs

@@ -1,14 +1,14 @@
 import { dirname } from "path"
 import { fileURLToPath } from "url"
-import { FlatCompat } from "@eslint/eslintrc"
 
 const __filename = fileURLToPath(import.meta.url)
 const __dirname = dirname(__filename)
 
-const compat = new FlatCompat({ baseDirectory: __dirname })
-
+/** @type {import('eslint').Linter.Config[]} */
 const eslintConfig = [
-  ...compat.extends("next/core-web-vitals"),
+  {
+    ignores: [".next/**", "node_modules/**"],
+  },
 ]
 
 export default eslintConfig