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/undo/confirmation.rs

@@ -0,0 +1,36 @@
+use super::types::UndoError;
+use std::io;
+
+pub trait ConfirmationStrategy {
+    fn confirm(&self) -> Result<bool, UndoError>;
+}
+
+pub struct StdinConfirmation;
+
+impl ConfirmationStrategy for StdinConfirmation {
+    fn confirm(&self) -> Result<bool, UndoError> {
+        eprint!("\nDo you want to undo these changes? [y/N]: ");
+
+        let mut input = String::new();
+        if io::stdin().read_line(&mut input).is_err() {
+            return Err(UndoError::InputReadFailed(
+                "Failed to read input. Undo cancelled.".to_string(),
+            ));
+        }
+
+        let input = input.trim().to_lowercase();
+        if input != "y" && input != "yes" {
+            return Err(UndoError::UserCancelled);
+        }
+
+        Ok(true)
+    }
+}
+
+pub struct AutoConfirm;
+
+impl ConfirmationStrategy for AutoConfirm {
+    fn confirm(&self) -> Result<bool, UndoError> {
+        Ok(true)
+    }
+}