update dockerfiles and github workflows

backend/Dockerfile

@@ -14,8 +14,7 @@ COPY package*.json ./
 
 # Install app dependencies using npm ci for faster, reliable builds
 # --only=production installs only production dependencies (including 'oui')
-RUN npm ci --only=production
-# REMOVED: RUN npm i oui (should be installed by npm ci now)
+RUN npm ci --omit=dev
 
 # Stage 2: Production Image
 FROM node:24-alpine

backend/package.json

@@ -9,6 +9,9 @@
   "keywords": [],
   "author": "",
   "license": "ISC",
+  "engines": {
+    "node": ">=24"
+  },
   "dependencies": {
     "@maxmind/geoip2-node": "^6.0.0",
     "@sentry/node": "^10.42.0",