Fix Ruff linting: Remove unused imports

- Remove unused imports from test files
- Fix F401 errors across multiple test modules

tests/unit/agents/test_market_analyst_extended.py

@@ -1,6 +1,6 @@
 """Extended unit tests for market analyst to improve coverage."""
 
-from unittest.mock import Mock, MagicMock, patch
+from unittest.mock import Mock
 import pytest
 
 

tests/unit/dataflows/test_utils.py

@@ -1,8 +1,5 @@
 """Unit tests for dataflows utils module."""
 
-from unittest.mock import Mock, patch
-import pytest
-from datetime import datetime
 
 
 class TestDataflowsUtils:

tests/unit/graph/test_propagation.py

@@ -1,6 +1,6 @@
 """Unit tests for propagation module."""
 
-from unittest.mock import Mock, patch
+from unittest.mock import Mock
 import pytest
 
 

tests/unit/graph/test_reflection.py

@@ -1,6 +1,6 @@
 """Unit tests for reflection module."""
 
-from unittest.mock import Mock, patch
+from unittest.mock import Mock
 import pytest
 
 

tests/unit/graph/test_signal_processing.py

@@ -1,7 +1,6 @@
 """Unit tests for signal processing module."""
 
 from unittest.mock import Mock, patch
-import pytest
 
 
 class TestSignalProcessor:
@@ -9,7 +8,7 @@ class TestSignalProcessor:
 
     def test_signal_processor_initialization(self):
         """Test SignalProcessor initialization."""
-        mock_llm = Mock()
+        # mock_llm would be used here but import is mocked
 
         # Import with mocked dependencies to avoid pandas import
         with patch(