refactor: rename MaterialsToBeDeleted to MaterialsTypeToBeDeleted

Rename database table and related classes from MaterialsToBeDeleted to MaterialsTypeToBeDeleted for better semantic clarity.

Changes:
- Rename MaterialsToBeDeletedDAO class to MaterialsTypeToBeDeletedDAO
- Update all SQL queries to reference MaterialsTypeToBeDeleted table
- Update import statement in material_status_validator.py
- Update documentation comments

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

db/materials_to_delete.py

@@ -19,7 +19,7 @@ def get_materials_to_delete(manager_name):
     """
     query = """
         SELECT [MaterialName]
-        FROM [dbo].[MaterialsToBeDeleted]
+        FROM [dbo].[MaterialsTypeToBeDeleted]
         WHERE [ManagerName] = ?
     """
 
@@ -39,7 +39,7 @@ def get_all_materials_to_delete() -> List[Dict[str, Any]]:
     """
     query = """
         SELECT [MaterialName], [ManagerName]
-        FROM [dbo].[MaterialsToBeDeleted]
+        FROM [dbo].[MaterialsTypeToBeDeleted]
         WHERE [MaterialName] IS NOT NULL
         ORDER BY [ManagerName], [MaterialName]
     """