fix: resolve CI/CD linting issues

- Remove unused imports (F401) from analyzers and test files
- Remove unused typing imports (Any, Dict, List, Optional)
- Remove unused datetime imports
- Remove unused rich.columns import
- Remove unused pytest imports in test files

src/analyzers/code_churn.py

@@ -1,9 +1,9 @@
 from collections import defaultdict
 from dataclasses import dataclass
-from typing import Any, Dict, List, Optional
+from typing import Dict, Optional
 
 from src.analyzers.git_repository import GitRepository
-from src.models.data_structures import CodeChurnAnalysis, Commit
+from src.models.data_structures import CodeChurnAnalysis
 
 
 @dataclass