fix: backend Dockerfile copies all files, server.js uses port 3000 for container consistency

backend/Dockerfile

@@ -14,8 +14,8 @@ COPY package*.json ./
 # Install dependencies
 RUN npm ci --only=production && npm cache clean --force
 
-# Copy application files
-COPY server.js ./
+# Copy all application files
+COPY . ./
 
 # Create logs directory and set permissions
 RUN mkdir -p logs && chown -R nodeapp:nodejs /app