Clarify the purpose of separate Docker resources (mastodon#30568)

Dockerfile

@@ -1,5 +1,8 @@
 # syntax=docker/dockerfile:1.7
 
+# This file is designed for production server deployment, not local development work
+# For a containerized local dev environment, see: https://github.com/mastodon/mastodon/blob/main/README.md#docker
+
 # Please see https://docs.docker.com/engine/reference/builder for information about
 # the extended buildx capabilities used in this file.
 # Make sure multiarch TARGETPLATFORM is available for interpolation

README.md

@@ -101,7 +101,9 @@ To set up **MacOS** for native development, complete the following steps:
 
 ### Docker
 
-For development with **Docker**, complete the following steps:
+For production hosting and deployment with **Docker**, use the `Dockerfile` and
+`docker-compose.yml` in the project root directory. To create a local
+development environment with **Docker**, complete the following steps:
 
 - Install Docker Desktop
 - Run `docker compose -f .devcontainer/docker-compose.yml up -d`

docker-compose.yml

@@ -1,3 +1,6 @@
+# This file is designed for production server deployment, not local development work
+# For a containerized local dev environment, see: https://github.com/mastodon/mastodon/blob/main/README.md#docker
+
 services:
   db:
     restart: always