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/plugins/built_in/system_management/plugin.py

@@ -295,7 +295,7 @@ class SystemCommand(PlusCommand):
             if injections:
                 response_parts.append(f"🎯 **{target}** (注入源):")
                 for inj in injections:
-                    source_tag = f"({inj['source']})" if inj['source'] != 'static_default' else ''
+                    source_tag = f"({inj['source']})" if inj["source"] != "static_default" else ""
                     response_parts.append(f"  ⎿ `{inj['name']}` (优先级: {inj['priority']}) {source_tag}")
             else:
                 response_parts.append(f"🎯 **{target}** (无注入)")