Fix: Downgrade to Express v4 and rebuild deps in Docker

Dockerfile

@@ -15,9 +15,9 @@ RUN npm run build
 FROM node:18-slim
 WORKDIR /app
 
-# Copy backend package config and install production dependencies
-COPY backend/package.json backend/package-lock.json* ./
-RUN npm ci --omit=dev
+# Copy package.json ONLY and install production dependencies from scratch
+COPY backend/package.json ./
+RUN npm install --omit=dev
 
 # Copy rest of the backend code
 COPY backend/ .

backend/package.json

@@ -19,7 +19,7 @@
     "aws-sdk": "^2.1692.0",
     "cors": "^2.8.5",
     "dotenv": "^17.0.1",
-    "express": "^5.1.0"
+    "express": "^4.19.2"
   },
   "devDependencies": {
     "nodemon": "^3.1.10"