chore: perform widespread code cleanup and formatting

Perform a comprehensive code cleanup across multiple modules to improve code quality, consistency, and maintainability.

Key changes include:
- Removing numerous unused imports.
- Standardizing import order.
- Eliminating trailing whitespace and inconsistent newlines.
- Updating legacy type hints to modern syntax (e.g., `List` -> `list`).
- Making minor improvements for code robustness and style.

src/llm_models/utils_model.py

@@ -537,7 +537,7 @@ class _PromptProcessor:
             else:
                 is_truncated = True
         return content, reasoning, is_truncated
-        
+
     @staticmethod
     async def _extract_reasoning(content: str) -> tuple[str, str]:
         """