Now with working validation and correction feedback

backend/app/row_storage.py

@@ -0,0 +1,12 @@
+class RowStorage:
+    def __init__(self):
+        self.data = {}
+
+    def get_row(self, row_num):
+        return self.data.get(row_num, {})
+
+    def set_row(self, row_num, row_data):
+        self.data[row_num] = row_data
+
+
+row_storage = RowStorage()  # Singleton instance for storing row data