[FEATURE] VLAN

[cachebag]

Is your feature request related to a problem? Please describe.
VLAN tagging is not supported. Users cannot create or manage VLAN interfaces (e.g., eth0.100) for network segmentation.

Describe the solution you'd like
Add support for creating and managing VLAN interfaces with configurable VLAN IDs and parent device selection.

For Developers- what would your solution be?

• Add NMVlan proxy trait in proxies.rs for org.freedesktop.NetworkManager.Device.Vlan
• Create vlan_builders.rs with build_vlan_connection() that accepts parent device and VLAN ID
• Add vlan.rs module with create_vlan(parent_interface, vlan_id) function
• Expose VLAN operations in NetworkManager public API
• Update DeviceType enum (VLAN type code: 19)

Additional context