Add property test cases

[secsovereign]

Description

Expand proptest coverage for transaction/block validation.

Context

Property-based testing helps discover edge cases and ensures our implementation handles a wide range of inputs correctly. We have some property tests but could expand coverage.

Acceptance Criteria

• Identify areas needing property test coverage
• Add property tests using proptest
• Ensure tests cover important invariants
• All new tests pass

Technical Details

• Files to modify: tests/property_*.rs or create new property test files
• Dependencies: proptest crate (already in dependencies)
• References: See existing property tests for patterns

Skills Required

• Property-based testing
• Rust
• Bitcoin protocol understanding

Difficulty

• Good First Issue
• Intermediate
• Advanced

Priority

• P0 (Critical - Blocks production)
• P1 (High - Important feature)
• P2 (Medium - Nice to have)
• P3 (Low - Future enhancement)

Getting Started

1. Review existing property tests in tests/
2. Identify consensus functions that would benefit from property testing
3. Write property tests using proptest
4. Run tests: cargo test --test property_*
5. Submit PR with new property tests