Static/utils.py

```python
import os
import time
import logging
from config import CONFIG

logger = logging.getLogger(__name__)

def clean_output_directory(max_age_seconds=86400):  # 24 hours
    """Remove output files older than max_age_seconds."""
    output_dir = os.path.join("static", "output")
    if not os.path.exists(output_dir):
        return
    
    current_time = time.time()
    for filename in os.listdir(output_dir):
        file_path = os.path.join(output_dir, filename)
        if os.path.isfile(file_path):
            file_age = current_time - os.path.getmtime(file_path)
            if file_age > max_age_seconds:
                try:
                    os.remove(file_path)
                    logger.info(f"Removed old output file: {file_path}")
                except Exception as e:
                    logger.error(f"Failed to remove {file_path}: {e}")

async def save_snapshot(frame, violation, output_dir):
    """Save a snapshot with metadata."""
    snapshot_filename = f"violation_{violation['violation']}_worker{violation['worker_id']}_{int(violation['timestamp']*100)}.jpg"
    snapshot_path = os.path.join(output_dir, snapshot_filename)
    cv2.imwrite(snapshot_path, frame, [cv2.IMWRITE_JPEG_QUALITY, CONFIG["SNAPSHOT_QUALITY"]])
    logger.info(f"Saved snapshot: {snapshot_path}")
    return snapshot_path, f"{CONFIG['PUBLIC_URL_BASE']}{snapshot_filename}"
```

Add a call to `clean_output_directory()` at the start of `process_video()` in `app.py`:

```python
async def process_video(video_data, temp_dir, progress=gr.Progress()):
    clean_output_directory()  # Clean old files before processing
    output_dir = os.path.join(temp_dir, "output")
    os.makedirs(output_dir, exist_ok=True)
    # ... rest of the function
```