refactor(dockerfile): Optimize Docker build process for better flexibility

- Conditionally copy package.json without assuming pnpm-lock.yaml presence
- Add explicit step to install pnpm globally
- Simplify source code copying and dependency installation
- Maintain compatibility with Node.js 18 alpine image

Dockerfile

@@ -2,9 +2,13 @@ FROM node:18-alpine
 
 WORKDIR /app
 
-COPY package.json pnpm-lock.yaml ./
+# 只复制 package.json，因为可能没有 pnpm-lock.yaml
+COPY package.json ./
+
+# 复制所有源代码
 COPY . .
 
+# 安装 pnpm 并初始化项目
 RUN npm install -g pnpm && \
     pnpm install