docker compose improvements

[haarg]

Fixes and improves a few things for docker compose:

• Specify a shorter COLUMNS value to try to prevent wrapping when used with docker compose in the foreground.
• Add a watch option to rebuild the image when the cpanfile is updated.
• Add a dependency on web-asset-build to web-server. This means if you specifically run the web-service, you'll still properly get the assets built.