[BUG] Service with `provider` type should not imply a network

[nigelpoulton]

Description

Compose apps with the new provider services such as Docker Model Runner cause Compose to create a default network for the project even though these types of services don't attach to container networks.

As these are used to define and manage service on external/non-container platforms I don't think they should connect to container networks.

Steps To Reproduce

1. The following Compose file.

networks:
  chatnet:
services:
  frontend:
    image: nigelpoulton/ps-dockerai:dmr-fe-0.1
    networks:
      - chatnet
    ports:
      - "3000:3000"
    env_file:
      - .env
    depends_on:
      - backend
  backend:
    image: nigelpoulton/ps-dockerai:dmr-be-0.1
    networks:
      - chatnet
    env_file:
      - .env
    depends_on:
      - dmr
  dmr:
    provider:
      type: model
      options:
        model: ${LLM_MODEL_NAME}

2. Start app with docker compose up --detach
3. List networks with docker network ls
4. The default network isn't needed so shouldn't be present

Compose Version

Docker Compose version v2.36.2-desktop.1

Docker Environment

Client:
 Version:    28.2.0-rc.2
 Context:    desktop-linux
 Debug Mode: false
 Plugins:
  ai: Docker AI Agent - Ask Gordon (Docker Inc.)
    Version:  v1.4.0
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-ai
  buildx: Docker Buildx (Docker Inc.)
    Version:  v0.24.0-desktop.2
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-buildx
  cloud: Docker Cloud (Docker Inc.)
    Version:  v0.3.9
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-cloud
  compose: Docker Compose (Docker Inc.)
    Version:  v2.36.2-desktop.1
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-compose
  debug: Get a shell into any image or container (Docker Inc.)
    Version:  0.0.41
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-debug
  desktop: Docker Desktop commands (Docker Inc.)
    Version:  v0.1.9
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-desktop
  extension: Manages Docker extensions (Docker Inc.)
    Version:  v0.2.29
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-extension
  init: Creates Docker-related starter files for your project (Docker Inc.)
    Version:  v1.4.0
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-init
  mcp: Docker MCP Plugin (Docker Inc.)
    Version:  dev
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-mcp
  model: Docker Model Runner (Docker Inc.)
    Version:  v0.1.24
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-model
  sbom: View the packaged-based Software Bill Of Materials (SBOM) for an image (Anchore Inc.)
    Version:  0.6.0
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-sbom
  scout: Docker Scout (Docker Inc.)
    Version:  v1.18.1
    Path:     /Users/nigelpoulton/.docker/cli-plugins/docker-scout

Server:
 Containers: 1
  Running: 0
  Paused: 0
  Stopped: 1
 Images: 5
 Server Version: 28.2.0-rc.2
 Storage Driver: overlayfs
  driver-type: io.containerd.snapshotter.v1
 Logging Driver: json-file
 Cgroup Driver: cgroupfs
 Cgroup Version: 2
 Plugins:
  Volume: local
  Network: bridge host ipvlan macvlan null overlay
  Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
 CDI spec directories:
  /etc/cdi
  /var/run/cdi
 Swarm: inactive
 Runtimes: runc io.containerd.runc.v2
 Default Runtime: runc
 Init Binary: docker-init
 containerd version: 05044ec0a9a75232cad458027ca83437aae3f4da
 runc version: v1.2.5-0-g59923ef
 init version: de40ad0
 Security Options:
  seccomp
   Profile: builtin
  cgroupns
 Kernel Version: 6.10.14-linuxkit
 Operating System: Docker Desktop
 OSType: linux
 Architecture: aarch64
 CPUs: 8
 Total Memory: 7.654GiB
 Name: docker-desktop
 ID: c78c3031-7514-4fa4-9839-571f8b83dad5
 Docker Root Dir: /var/lib/docker
 Debug Mode: false
 HTTP Proxy: http.docker.internal:3128
 HTTPS Proxy: http.docker.internal:3128
 No Proxy: hubproxy.docker.internal
 Labels:
  com.docker.desktop.address=unix:///Users/nigelpoulton/Library/Containers/com.docker.docker/Data/docker-cli.sock
 Experimental: false
 Insecure Registries:
  hubproxy.docker.internal:5555
  ::1/128
  127.0.0.0/8
 Live Restore Enabled: false

WARNING: DOCKER_INSECURE_NO_IPTABLES_RAW is set

Anything else?

No response