Add LeetCode solution 3043

[eselyavka]

Summary

• add LeetCode solution 3043 under practice/leetcode/solutions_03000/
• implement longest common prefix lookup using integer prefix truncation
• add inline unit tests for matching and non-matching prefix cases

Testing

• ~/.venv/py3_11/bin/python -m pytest practice/leetcode/solutions_03000/solution_03043.py
• git commit hook: full pytest suite
• git commit hook: pylint on changed Python files