v0.3.0-rc15

perf: Add parallel processing for search operations

This commit significantly improves search performance by:

- Adding parallel block processing in file_processing.rs using Rayon
- Creating a new block_optimization.rs module for merging adjacent line ranges
- Implementing parallel file processing in search_runner.rs
- Optimizing memory usage with thread-safe data structures (Arc/Mutex)
- Adding filtering for lines longer than 500 characters
- Using dynamic thread count based on system capabilities
- Adding comprehensive tests for parallel search operations

Additional improvements:
- Code cleanup and formatting fixes
- Removal of unused imports and duplicate code
- Better error handling for thread-safe operations
- Improved documentation with examples