feat: per-interface Wi-Fi scoping for multi-radio systems

[cachebag]

This PR adds per-interface Wi-Fi scoping for multi-radio systems and bumps to 3.0.

Added

• WifiDevice, list_wifi_devices(), wifi_device_by_interface()
• WifiScope via nm.wifi("wlan1") — scan / list_networks / list_access_points / connect / connect_to_bssid / disconnect / set_enabled / forget all pinned to one radio
• set_wifi_enabled(interface, bool) for per-radio enable/disable (uses Device.Autoconnect + Device.Disconnect(), independent of the global wireless killswitch)
• WifiInterfaceNotFound, NotAWifiDevice errors
• examples/multi_wifi.rs

Breaking changes

• connect, connect_to_bssid, disconnect, scan_networks, list_networks take an interface: Option<&str> argument (None = previous behavior)
• set_wifi_enabled now requires (interface, bool)
• Removed deprecated wifi_enabled(), wifi_hardware_enabled(), no-arg set_wifi_enabled(bool) — use wifi_state() / set_wireless_enabled()
• disconnect now correctly only deactivates active connections owned by the targeted device (was deactivating every active connection)

Migration

Old	New
nm.connect(ssid, creds)	nm.connect(ssid, None, creds)
nm.connect_to_bssid(ssid, bssid, creds)	nm.connect_to_bssid(ssid, bssid, None, creds)
nm.disconnect()	nm.disconnect(None)
nm.scan_networks() / nm.list_networks()	add (None)
nm.set_wifi_enabled(true)	nm.set_wireless_enabled(true)
nm.wifi_enabled() / wifi_hardware_enabled()	nm.wifi_state()