chore(lint): apply ruff --fix (4443 auto-fixes)

Auto-fixed categories:
- F401: unused imports removed
- I001: import blocks sorted
- W293: trailing whitespace stripped
- UP035: deprecated typing imports replaced
- SIM: simplify suggestions applied
- ARG: unused args prefixed with underscore
- T201: print statements removed
- F841: unused variables removed
- RUF059: unpacked variables prefixed

Remaining ~1500 unfixable errors (C901, B904, N806, E402) require manual work.

Backend smoke tests: 13/13 passed.

backend/tests/test_smoke_plugins.py

@@ -1,9 +1,10 @@
+import os
 import sys
 from pathlib import Path
-import os
-import pytest
 from unittest.mock import MagicMock, patch
 
+import pytest
+
 sys.path.insert(0, str(Path(__file__).parent.parent))
 
 # Mock database before any modules that import it are loaded
@@ -22,18 +23,18 @@ class TestPluginSmoke:
         syntax errors, missing class declarations).
         """
         from src.core.plugin_loader import PluginLoader
-        
+
         plugin_dir = os.path.join(str(Path(__file__).parent.parent), "src", "plugins")
-        
+
         # This will discover and instantiate plugins
         loader = PluginLoader(plugin_dir)
 
         plugins = loader.get_all_plugin_configs()
         plugin_ids = {p.id for p in plugins}
-        
+
         # We expect at least the migration and git plugins to be present
         expected_plugins = {"superset-migration", "git-integration"}
-        
+
         missing_plugins = expected_plugins - plugin_ids
         assert not missing_plugins, f"Missing expected plugins: {missing_plugins}"
 
@@ -44,21 +45,21 @@ class TestPluginSmoke:
         """
         from src.core.plugin_loader import PluginLoader
         from src.core.task_manager.manager import TaskManager
-        
+
         plugin_dir = os.path.join(str(Path(__file__).parent.parent), "src", "plugins")
         loader = PluginLoader(plugin_dir)
-        
+
         # Initialize TaskManager with real loader
         with patch("src.core.task_manager.manager.TaskPersistenceService") as MockPersistence, \
              patch("src.core.task_manager.manager.TaskLogPersistenceService"):
-             
+
             MockPersistence.return_value.load_tasks.return_value = []
-            
+
             with patch("src.dependencies.config_manager"):
                 manager = TaskManager(loader)
-            
+
             # Stop the flusher thread to prevent hanging
             manager._flusher_stop_event.set()
             manager._flusher_thread.join(timeout=2)
-            
+
             assert manager is not None