fix: Update Node.js to v20 in all Dockerfiles and regenerate server package-lock.json

- Node 20 required for Colyseus 0.16+
- Update npm ci flags for compatibility
- Regenerate package-lock.json to sync missing dependencies

server/Dockerfile

@@ -1,5 +1,5 @@
 # Server Dockerfile - Colyseus Server
-FROM node:18-alpine
+FROM node:20-alpine
 
 # Set working directory
 WORKDIR /app
@@ -8,7 +8,7 @@ WORKDIR /app
 COPY package*.json ./
 
 # Install dependencies
-RUN npm ci --only=production
+RUN npm ci --omit=dev
 
 # Copy source code
 COPY . .