chore: migrate from npm to pnpm

Dockerfile

@@ -1,6 +1,7 @@
 FROM node:22-alpine
+RUN corepack enable && corepack prepare pnpm@11.1.1 --activate
 WORKDIR /app
-COPY package*.json ./
-RUN npm install
+COPY package.json pnpm-lock.yaml ./
+RUN pnpm install --frozen-lockfile
 COPY . .
 CMD ["node", "server.js"]