optimized

feat(core): add multi-threaded URL processing for screenshots

- Refactor main program to support asynchronous execution with async Task Main
- Introduce --threads/-t option to specify number of concurrent threads (default 10)
- Implement URL partitioning to distribute workload evenly among threads
- Each thread creates its own WebDriver instance for thread safety
- Add ProcessUrlsWithThreads function to manage parallel screenshot tasks
- Update logging to be thread-safe with locking and async file writing
- Enhance protocol fallback handling on "Bad Request" responses
- Create more robust command line argument parsing including new options
- Update help text and README to document multi-threading and new parameters
- Preserve backward compatibility by allowing single-threaded sequential processing
- Improve screenshot file naming to sanitize and truncate filenames appropriately