Refactor Node initialization and update methods

Refactor Node class to properly initialize value and improve type hints. Update PersistentSegmentTree methods for better clarity and maintainability.

Author: cclauss

data_structures/binary_tree/persistent_segment_tree.py

@@ -5,7 +5,7 @@
 
 @dataclass
 class Node:
-    value: int = value
+    value: int
     left: Node | None = None
     right: Node | None = None