fix: set Docker API version for Watchtower compatibility

Add DOCKER_API_VERSION=1.44 environment variable to Watchtower
to ensure compatibility with upgraded Docker daemon.

The Watchtower image (v1.7.1) has an older Docker client that
defaults to API version 1.25, which is incompatible with the
new Docker daemon requiring API version 1.44+.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

net/compose.yaml

@@ -154,6 +154,8 @@ services:
     volumes:
       - /var/run/docker.sock:/var/run/docker.sock
     environment:
+      # Docker API version negotiation
+      DOCKER_API_VERSION: "1.44"
       # Check for updates every 5 minutes (300 seconds)
       WATCHTOWER_POLL_INTERVAL: ${WATCHTOWER_POLL_INTERVAL:-300}
       # Only update containers with the watchtower label