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/person_info/relationship_fetcher.py

@@ -269,7 +269,7 @@ class RelationshipFetcher:
             platform = "unknown"
             if existing_stream:
                 # 从现有记录获取platform
-                platform = getattr(existing_stream, 'platform', 'unknown') or "unknown"
+                platform = getattr(existing_stream, "platform", "unknown") or "unknown"
                 logger.debug(f"从现有ChatStream获取到platform: {platform}, stream_id: {stream_id}")
             else:
                 logger.debug(f"未找到现有ChatStream记录，使用默认platform: unknown, stream_id: {stream_id}")