feat: 优化 Dockerfile 以提高构建效率，并添加 .npmrc 配置文件

Author: Rabithua

backend/.npmrc

@@ -0,0 +1,2 @@
+registry=https://registry.npmjs.org/
+legacy-peer-deps=true

backend/Dockerfile

@@ -1,21 +1,21 @@
 # Use a smaller base image
 FROM node:22.15.0-alpine
 
-
 # Install OpenSSL
 RUN apk add --no-cache openssl
 
 # Set working directory
 WORKDIR /app
 
-# Copy project files
-COPY . .
-
-# Generate Prisma client
-RUN npm config set registry https://registry.npmmirror.com/
+# Copy package files and npm config first for better caching
+COPY package*.json .npmrc ./
 
+# Install dependencies
 RUN npm install --omit=dev
 
+# Copy rest of the project files
+COPY . .
+
 # Expose container port 3000
 EXPOSE 3000