Implement streaming pipeline endpoint for batch processing

- Added `/run/streaming-pipeline` endpoint to process data in batches from either a database or CSV file.
- Introduced `BatchResponse` model for structured responses.
- Updated README with new endpoint details, including parameters and example usage.
- Enhanced error handling and logging during batch processing.
- Ensured data preprocessing and NaN handling in analysis functions.

salary_analytics/data_loader.py

@@ -69,6 +69,7 @@ class DataLoader:
                         'd4': 'customer_id'
                     })
                 
+                chunk = chunk.dropna()
                 chunks.append(chunk)
             
             # Combine all chunks
@@ -127,6 +128,7 @@ class DataLoader:
                     'd4': 'customer_id'
                 })
                 
+                chunk = chunk.dropna()
                 chunks.append(chunk)
                 offset += self.chunk_size