Extract common S3 operation patterns into reusable functions

[Asi0Flammeus]

Description

S3 endpoints contain duplicated patterns for download/upload operations that should be extracted into reusable utilities.

Current Duplication

Similar code patterns repeated across:

• /translate/pptx_s3
• /translate/text_s3
• /transcribe/audio_s3
• /translate/course_s3

Common Patterns

1. Download files from S3 to local temp directory
2. Process files with different tools
3. Upload results back to S3
4. Progress tracking and error handling
5. Task status management

Proposed Utilities

async def process_s3_files(
    input_keys: List[str],
    processor_func: Callable,
    output_prefix: Optional[str],
    task_id: str,
    **processor_kwargs
) -> List[str]:
    """Generic S3 file processing pipeline"""

async def download_s3_batch(keys: List[str], temp_dir: Path) -> List[Path]:
    """Download multiple files from S3"""

async def upload_s3_batch(files: List[Path], prefix: str) -> List[str]:
    """Upload multiple files to S3"""

Requirements

• Extract common download/upload patterns
• Create generic file processing pipeline
• Maintain progress tracking functionality
• Preserve error handling behavior
• Add comprehensive type hints
• Include proper documentation

Benefits

• Eliminates code duplication
• Consistent error handling across endpoints
• Easier to add new S3 operations
• Better testability of S3 operations
• Simplified endpoint implementations

Acceptance Criteria

• Common S3 patterns extracted to utilities
• All S3 endpoints use shared functions
• No loss of functionality during refactor
• Progress tracking preserved
• Error handling consistent

Related

• Code quality improvement from PR Create API endpoints for contribute app #22 review
• Supports easier testing and maintenance

Priority

Medium - Code quality and maintainability