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/modes_test.rs

@@ -1,4 +1,3 @@
-use markbase::filetree::node::NodeType;
 use markbase::filetree::{mode, FileTree};
 use rusqlite::Connection;
 use uuid::Uuid;
@@ -102,7 +101,7 @@ fn test_mode_sort_options() {
     let mode = mode::get_mode("list").unwrap();
     let sort_options = mode.sort_options();
 
-    assert!(sort_options.len() > 0, "sort options should not be empty");
+    assert!(!sort_options.is_empty(), "sort options should not be empty");
 }
 
 #[test]
@@ -111,7 +110,7 @@ fn test_mode_filter_options() {
     let filter_options = mode.filter_options();
 
     assert!(
-        filter_options.len() > 0,
+        !filter_options.is_empty(),
         "filter options should not be empty"
     );
 }