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

Dockerfile

@@ -1,11 +1,13 @@
 # Stage 1: Install dependencies
 FROM node:22-alpine AS deps
+RUN apk add --no-cache espeak-ng
 WORKDIR /app
 COPY package.json package-lock.json ./
 RUN npm ci
 
 # Stage 2: Build
 FROM node:22-alpine AS builder
+RUN apk add --no-cache espeak-ng
 WORKDIR /app
 COPY --from=deps /app/node_modules ./node_modules
 COPY . .
@@ -15,18 +17,21 @@ RUN npm run build
 
 # Stage 3: Production
 FROM node:22-alpine AS runner
+RUN apk add --no-cache espeak-ng
 WORKDIR /app
 
 ENV NODE_ENV=production
 ENV NEXT_TELEMETRY_DISABLED=1
 
-RUN addgroup --system --gid 1001 nodejs
+RUN addgroup --system --gid 1001 nextjs
 RUN adduser --system --uid 1001 nextjs
+RUN adduser nextjs nextjs
 
 COPY --from=builder /app/public ./public
-COPY --from=builder --chown=nextjs:nodejs /app/.next/standalone ./
-COPY --from=builder --chown=nextjs:nodejs /app/.next/static ./.next/static
-COPY --from=builder --chown=nextjs:nodejs /app/prisma ./prisma
+COPY --from=builder --chown=nextjs:nextjs /app/.next/standalone ./
+COPY --from=builder --chown=nextjs:nextjs /app/.next/static ./.next/static
+COPY --from=builder --chown=nextjs:nextjs /app/prisma ./prisma
+COPY --from=builder --chown=nextjs:nextjs /app/node_modules/.prisma ./node_modules/.prisma
 
 USER nextjs