Add Docker cache cleaning

[momenbasel]

Add a cleaning category for Docker caches and unused images.

Paths to clean:

• ~/Library/Containers/com.docker.docker/Data/vms/ - Docker VM disk images
• ~/.docker/ - Docker config caches

Implementation:

• Add a new CleaningCategory case
• Scan for Docker-related cache directories
• Display size and allow selective cleanup

This is a good starting point for contributors who use Docker on macOS.