LeetCode 208: Implement Trie (Prefix Tree)

## [LeetCode 208: Implement Trie (Prefix Tree)](https://leetcode.com/problems/implement-trie-prefix-tree/)

**Difficulty:** Medium
**Category:** Trie

### Tasks
- [ ] Implement solution in `src/trie/implement_trie_prefix_tree.py`
- [ ] Verify tests pass: `pytest tests/test_implement_trie_prefix_tree.py`
- [ ] Analyze time and space complexity