fix(main.py): release video capture before moving files to prevent errors

main.py

@@ -92,6 +92,7 @@ class MediaGrader:
         for file in media_files:
             # Check if file is not in a grade directory (1-5)
             if not any(part in ["1", "2", "3", "4", "5"] for part in file.parts):
+                print("Adding file: ", file)
                 filtered_files.append(file)
 
         return sorted(filtered_files)
@@ -375,6 +376,11 @@ class MediaGrader:
         # Track this move for undo functionality BEFORE making changes
         self.undo_history.append((str(destination), str(current_file), self.current_index))
 
+        # Release video capture to unlock the file before moving
+        if self.current_cap:
+            self.current_cap.release()
+            self.current_cap = None
+
         try:
             shutil.move(str(current_file), str(destination))
             print(f"Moved {current_file.name} to grade {grade}")
@@ -404,6 +410,11 @@ class MediaGrader:
         # Get the last action
         moved_file_path, original_file_path, original_index = self.undo_history.pop()
         
+        # Release video capture to unlock any current file before moving
+        if self.current_cap:
+            self.current_cap.release()
+            self.current_cap = None
+        
         try:
             # Move the file back to its original location
             shutil.move(moved_file_path, original_file_path)