Update agent setup instructions with Watchtower auto-updates

- Change default agent image to gmcintire/towerops-agent:main
- Add Watchtower service to docker-compose instructions
- Configure 15-minute update check interval for development
- Add DOCKER_API_VERSION=1.44 to prevent API compatibility errors
- Remove deprecated docker-compose version field

config/config.exs

@@ -88,7 +88,7 @@ config :towerops, :scopes,
 # Agent Docker Image
 # Override this in runtime.exs or environment-specific config
 config :towerops,
-  agent_docker_image: "towerops/agent:latest"
+  agent_docker_image: "gmcintire/towerops-agent:main"
 
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.

lib/towerops_web/live/agent_live/index.html.heex

@@ -257,6 +257,8 @@
       - WATCHTOWER_LABEL_ENABLE=true
       - WATCHTOWER_CLEANUP=true
       - WATCHTOWER_LOG_LEVEL=info
+      # Use latest Docker API version
+      - DOCKER_API_VERSION=1.44
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock</code></pre>
                 <button
@@ -290,6 +292,8 @@
       - WATCHTOWER_LABEL_ENABLE=true
       - WATCHTOWER_CLEANUP=true
       - WATCHTOWER_LOG_LEVEL=info
+      # Use latest Docker API version
+      - DOCKER_API_VERSION=1.44
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock</textarea>
               </div>