chore(docker): switch to pnpm, update Dockerfile, docker-compose, and README

Dockerfile

@@ -1,23 +1,15 @@
-# Use official Node.js LTS image
 FROM node:18-alpine
 
-# Create app directory
 WORKDIR /app
 
-# Install build dependencies and copy manifest
-RUN apk add --no-cache python3 make g++
+RUN apk add --no-cache python3 make g++ pnpm
 
 COPY package.json pnpm-lock.yaml ./
 
-# Install dependencies
-RUN npm ci
+RUN pnpm install --frozen-lockfile
 
-# Copy source code
 COPY . .
 
-# Expose no ports (Discord bot)
-# Define default environment variables (optional)
 ENV NODE_ENV=production
 
-# Start the bot
-CMD ["node", "src/index.js"]
+CMD [node, src/index.js]