docker: update docker-compose file.

* Listen on port 3000 instead of port 80. Port 80 is prone to conflicts
  with other webservers.

* Use the production version of the Danbooru Docker image. It's less
  likely to have bugs than master.

* Fix the autoinstall script to work with `curl ... | sh`.

* Lower PUMA_WORKERS to 1 to reduce memory usage.

docker-compose.yaml

@@ -1,7 +1,7 @@
 # A Docker Compose file that launches a minimal Danbooru instance. This is
 # suitable as a quick demo or for personal use, not for public-facing sites.
 #
-# This will start a Danbooru instance running on http://localhost.
+# This will start a Danbooru instance running on http://localhost:3000.
 #
 # Usage:
 #
@@ -22,28 +22,28 @@ version: "3.4"
 services:
   danbooru:
     user: root
-    image: ghcr.io/danbooru/danbooru
+    image: ghcr.io/danbooru/danbooru:production
     ports:
-      - "80:3000"
+      - "3000:3000"
     environment:
       - RAILS_ENV=production
       - RAILS_SERVE_STATIC_FILES=true
+      - PUMA_WORKERS=1
       - DATABASE_URL=postgresql://danbooru@postgres/danbooru
       - DANBOORU_REDIS_URL=redis://redis:6379
       - DANBOORU_IQDB_URL=http://iqdb:5588
-      - DANBOORU_CANONICAL_URL=http://localhost
+      - DANBOORU_CANONICAL_URL=http://localhost:3000
     volumes:
       - "danbooru-images:/danbooru/public/data"
     tmpfs:
       - /tmp
     depends_on:
       - postgres
-    command: ["bash", "-c", "bin/rails db:setup; bin/rails db:migrate && bin/rails server -b 0.0.0.0"]
-    user: root
+    command: ["bash", "-c", "bin/rails db:prepare && bin/rails server -b 0.0.0.0"]
 
   cron:
     user: root
-    image: ghcr.io/danbooru/danbooru
+    image: ghcr.io/danbooru/danbooru:production
     environment:
       - RAILS_ENV=production
       - DATABASE_URL=postgresql://danbooru@postgres/danbooru
@@ -59,7 +59,7 @@ services:
   delayed_jobs:
     # We need root to write temp upload files in the images directory (/danbooru/public/data)
     user: root
-    image: ghcr.io/danbooru/danbooru
+    image: ghcr.io/danbooru/danbooru:production
     environment:
       - RAILS_ENV=production
       - DATABASE_URL=postgresql://danbooru@postgres/danbooru