feat: add DocSplitterClient and GenericUnstractClient support

Add support for two new API patterns:
1. Doc-splitter APIs (job_id-based workflow)
2. Generic Unstract APIs (execution_id-based workflow)

## New Features

### DocSplitterClient
- File upload with form-data support
- Job status polling with configurable intervals
- Binary file download (zip files)
- Methods: upload(), get_job_status(), download_result(), wait_for_completion()

### GenericUnstractClient
- Dynamic endpoint support (invoice, contract, receipt, etc.)
- Execution ID-based tracking
- Multipart form-data uploads with 'files' field
- Methods: process(), get_result(), wait_for_completion(), check_status()

## Implementation Details
- Both clients follow existing patterns for consistency
- Comprehensive test coverage (55 new tests)
- Full type safety with proper error handling
- Updated README with usage examples and API documentation
- All clients share the same ApiHubClientException

## Testing
- 94/94 tests passing
- Comprehensive coverage of success/failure paths
- Performance benchmarks included
- Real-world usage scenarios tested

Author: jaseemjaskp

CLAUDE.md

@@ -65,3 +65,5 @@ This document contains critical information about working with this codebase. Fo
    - Follow existing patterns
    - Test thoroughly
    - Use Context7 mcp server if available to get latest documents.
+
+- Don't mention claude code any where in code, commit messages or in PR description or comment