PROPERLY fix the Docker icon in the main left sidebar navigation by updating the DockerIcon component to use lucide's Container icon instead of Simple Icons Docker logo.
Also revert incorrect changes that added Docker to the Proxmox sub-navigation tabs - Docker should not be in the Proxmox settings sub-menu.
Replace DockerIcon (Simple Icons) with lucide-solid's Container icon to maintain consistency with other navigation icons (Server, HardDrive, Mail). All icons now use the same stroke-based style and rendering pattern.
Add Docker tab to the settings section navigation using the same DockerIcon component used in the main navigation. The icon is rendered at w-4 h-4 to match the visual weight of the lucide icons at size 16.
Now the settings navigation shows: Virtual Environment, Backup Server, Mail Gateway, and Docker.