chore: simplify to plain JS worker.js and finalize install instructions

Dockerfile

@@ -7,9 +7,8 @@ RUN apk add --no-cache docker-cli
 WORKDIR /app
 
 COPY package*.json ./
-RUN npm install
+RUN npm install --production
 
 COPY . .
 
-# Run using the start script (tsx apps/worker/main.ts)
-CMD ["npm", "start"]
+CMD ["npm", "start"]