refactor: reorganize file operations and extract test modules

- Extract mover and undo functionality into dedicated modules (mover/ and undo/ subdirectories)
- Move cross-platform file operations to separate file_ops.rs module for reusability
- Extract batch and categorizer tests into separate test files (batch_test.rs, categorizer_test.rs)
- Refactor orchestrator.rs with extracted helper functions for improved readability
  - Separate cache and undo log initialization
  - Extract path resolution and offline mode determination logic
  - Simplify main organization flow by delegating to helper functions
- Update module exports to expose new types and functions (MoveError, MoveSummary, UndoError, UndoSummary)
- Reduce code duplication of move_file_cross_platform implementation

src/files/batch_test.rs

@@ -0,0 +1,62 @@
+use super::*;
+use std::fs::{self, File};
+use std::path::Path;
+
+#[test]
+fn test_file_batch_from_path() {
+    let temp_dir = tempfile::tempdir().unwrap();
+    let dir_path = temp_dir.path();
+
+    File::create(dir_path.join("file1.txt")).unwrap();
+    File::create(dir_path.join("file2.rs")).unwrap();
+    fs::create_dir(dir_path.join("subdir")).unwrap();
+
+    let batch = FileBatch::from_path(dir_path, false);
+    assert_eq!(batch.count(), 2);
+    assert!(batch.filenames.contains(&"file1.txt".to_string()));
+    assert!(batch.filenames.contains(&"file2.rs".to_string()));
+}
+
+#[test]
+fn test_file_batch_from_path_nonexistent() {
+    let batch = FileBatch::from_path(Path::new("/nonexistent/path"), false);
+    assert_eq!(batch.count(), 0);
+}
+
+#[test]
+fn test_file_batch_from_path_non_recursive() {
+    let temp_dir = tempfile::tempdir().unwrap();
+    let dir_path = temp_dir.path();
+    File::create(dir_path.join("file1.txt")).unwrap();
+    File::create(dir_path.join("file2.rs")).unwrap();
+    fs::create_dir(dir_path.join("subdir")).unwrap();
+    File::create(dir_path.join("subdir").join("file3.txt")).unwrap();
+    let batch = FileBatch::from_path(dir_path, false);
+    assert_eq!(batch.count(), 2);
+    assert!(batch.filenames.contains(&"file1.txt".to_string()));
+    assert!(batch.filenames.contains(&"file2.rs".to_string()));
+    assert!(!batch.filenames.contains(&"subdir/file3.txt".to_string()));
+}
+
+#[test]
+fn test_file_batch_from_path_recursive() {
+    let temp_dir = tempfile::tempdir().unwrap();
+    let dir_path = temp_dir.path();
+    File::create(dir_path.join("file1.txt")).unwrap();
+    fs::create_dir(dir_path.join("subdir1")).unwrap();
+    File::create(dir_path.join("subdir1").join("file2.rs")).unwrap();
+    fs::create_dir(dir_path.join("subdir1").join("nested")).unwrap();
+    File::create(dir_path.join("subdir1").join("nested").join("file3.md")).unwrap();
+    fs::create_dir(dir_path.join("subdir2")).unwrap();
+    File::create(dir_path.join("subdir2").join("file4.py")).unwrap();
+    let batch = FileBatch::from_path(dir_path, true);
+    assert_eq!(batch.count(), 4);
+    assert!(batch.filenames.contains(&"file1.txt".to_string()));
+    assert!(batch.filenames.contains(&"subdir1/file2.rs".to_string()));
+    assert!(
+        batch
+            .filenames
+            .contains(&"subdir1/nested/file3.md".to_string())
+    );
+    assert!(batch.filenames.contains(&"subdir2/file4.py".to_string()));
+}