fix(ci) : pin node:22-alpine instead of lts (now node 24 / npm 11)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

infra/prod/Dockerfile

@@ -22,7 +22,7 @@ COPY src src/
 RUN composer dump-autoload --optimize --no-dev
 
 # --- Stage 2: Build frontend ---
-FROM node:lts-alpine AS frontend-build
+FROM node:22-alpine AS frontend-build
 
 WORKDIR /app/frontend
 COPY frontend/package.json frontend/package-lock.json ./