fix(gui): resolve Tkinter RIGHT/LEFT constant collision

[houtan-rocky]

Fixes _tkinter.TclError: bad side "-1" caused by AIMA's internal RIGHT = -1 overriding tkinter.RIGHT due to wildcard imports.
Replaced from tkinter import * with import tkinter as tk and prefixed all Tkinter calls to isolate namespaces.

• Affected file: gui/romania_problem.py
• Python 3.4+ compliant
• No functional or layout changes
• Tested on Python 3.10–3.13 (Windows)

[houtan-rocky]

@darius @josd @orsenthil @soimort