Refactor async logging logic in report generation.

Removed unused log yielding in `main.py` to simplify the flow. Updated `send_json` in `deepresearch.py` to use an async generator for more flexible streaming of log data.

src/main.py

@@ -38,8 +38,6 @@ async def get_report_endpoint(request: ReportRequest):
             # Call the asynchronous get_report function
             generator = ReportGenerator(request.query, request.report_type)
             await generator.generate_report()
-            async for log in generator:
-                yield log
         except Exception as e:
             yield f"Error: {str(e)}"