Implements clickable name field with inline URL editor for Docker resources, matching the Proxmox guest URL feature:
- Create DockerMetadataAPI for storing custom URLs
- Add metadata loading and caching in DockerHosts component
- Add URL editing UI to DockerContainerRow and DockerServiceRow
- Global editing state prevents multiple simultaneous edits
- Shows external link icon when URL is set
- Supports Enter to save, Escape to cancel
- Toast notifications for save/delete operations
- Stores metadata with format: {hostId}:container:{containerId}
Allows users to add quick links to container/service dashboards (e.g., Portainer, Traefik, internal UIs).
