Fix disk detection and network configuration in AutoInstaller GUI

- Implement same disk detection logic as auto-installer.sh for detect_usb_device and detect_target_disk
- Use subprocess calls to lsblk, df, and mount point checks for accurate USB boot device detection
- Filter target disks by size (>4GB) and exclude USB boot device
- Add comprehensive network interface detection dialog
- Support both Ethernet and Wireless interfaces with full WiFi configuration
- Implement WiFi scanning, SSID selection, security type selection (WPA/WEP/Open)
- Add static IP configuration with IP address, gateway, and DNS settings
- Generate proper /etc/network/interfaces file for installed system
- Handle WiFi configuration with wireless-essid, wpa-passphrase, and wireless-key
- Apply network configuration to target system during installation

This resolves the issues where GUI failed to detect correct installation disk
and provides full network configuration capabilities including WiFi support.