Feat/contains duplicate

[mariocodecr]

📝 Pull Request Title

🛠️ Issue

• Closes [FEAT]: Contains Duplicate Implementation in Cairo #217

📖 Description

This PR implements a complete solution to the classic "Contains Duplicate" problem in Cairo v1, providing two different algorithmic approaches with comprehensive testing and
documentation.

Key Features:

• Naive O(n²) approach: Uses nested loops with early exit optimization for simplicity and O(1) space complexity
• Optimized O(n) approach: Leverages Cairo's Felt252Dict as a hash set for linear time complexity
• Comprehensive test suite: 21 tests covering all required examples, edge cases, and performance scenarios
• Production-ready code: Clean, well-documented Cairo v1 with senior-level mentoring comments
• Educational value: Clear complexity analysis and Cairo-specific implementation notes

Implementation Details:

• Both approaches work with Span for memory-efficient read-only array access
• Early exit optimization in both solutions returns immediately when duplicates are found
• Dict-based approach uses status tracking (0 = not seen, 1 = seen) for efficient duplicate detection
• All functions handle edge cases: empty arrays, single elements, and various duplicate positions

Required Examples Covered:

• [1,2,3,1] → true ✅
• [1,2,3,4] → false ✅
• [1,1,1,3,3,4,3,2,4,2] → true ✅

🖼️ Screenshots (if applicable)

• Include any relevant screenshots or examples of the changes made. This helps reviewers visualize the updates

📝 Additional Notes

• Complexity Analysis: Detailed time/space complexity comparison in README with performance recommendations
• Cairo Best Practices: Proper use of felt252, Span, and Felt252Dict following Cairo v1 conventions
• Educational Value: Code includes mentoring-level comments explaining algorithmic choices and Cairo-specific considerations
• Test Coverage: Comprehensive suite testing base cases, required examples, edge cases, and stress scenarios
• Documentation: Complete README with usage examples, build instructions, and when to use each approach