build(docker): add Dockerfile, Docker Compose config, and update README

Dockerfile

@@ -0,0 +1,23 @@
+# 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++
+
+COPY package.json pnpm-lock.yaml ./
+
+# Install dependencies
+RUN npm ci
+
+# 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"]