Switch to pre-built Docker Hub image for production

- Push app image to jpscott84/drinktracker on Docker Hub
- docker-compose.prod.yml uses image instead of build
- install.sh pulls image instead of building from source
- Much faster deploys (no npm ci/build on target server)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.prod.yml

@@ -63,9 +63,7 @@ services:
     restart: "no"
 
   app:
-    build:
-      context: .
-      dockerfile: Dockerfile
+    image: jpscott84/drinktracker:latest
     restart: unless-stopped
     ports:
       - "3000:3000"