fix: resolve clippy warnings and test errors

- Implement FromStr trait for NodeType instead of custom from_str method
- Fix redundant_closure warning in server.rs:455
- Add #[allow(clippy::too_many_arguments)] for new_file_node
- Fix unused variables in tests (_user_id, _conn)
- Remove unused imports (NodeType, serde_json::json)
- Replace len() > 0 with !is_empty() for clarity
- Replace == false with negation operator
- Format code with cargo fmt

tests/audio_test.rs

@@ -33,7 +33,7 @@ fn test_audio_devices_macos() {
     let (out, inp, co, ci) = audio_devices();
 
     //至少應該有一些輸出裝置（即使是內建的）
-    assert!(out.len() > 0 || inp.len() > 0);
+    assert!(!out.is_empty() || !inp.is_empty());
 
     // current應該是有效的字符串
     assert!(!co.is_empty() || !ci.is_empty());