Refactor VenomAge: fix bugs, add error handling, input validation, an…

[batukapicioglu]

…d UX improvements

• Fix duplicate if/elif conditions (elif never executed) in inter() and inter1()
• Fix duplicate netmask condition in ipchan() (second 255.255.255.0 check)
• Remove unused mac variable in inter1(); fix trailing spaces in MAC list
• Fix typo "Rondom" -> "Random" in labels and button text
• Add root permission check at startup with clear error message
• Add validate_mac() and validate_ip() helper functions with regex
• Add generate_random_mac() that generates IEEE-compliant random MACs
• Add get_current_mac() and get_current_ip() to display current values
• Replace deprecated subprocess.call() with subprocess.run() + return code checks
• Wrap all subprocess calls in try-except for proper error reporting
• Replace tk.Tk() destroy/recreate anti-pattern with tk.Toplevel + form.withdraw()
• Replace Entry fields with ttk.Combobox populated from /sys/class/net/ for interfaces
• Add confirmation dialogs before applying network changes
• Show current MAC/IP address on interface selection