feat: add __iter__ support to LayoutElements and Elements for native iteration

[pira998]

📝 PR Description:

This PR addresses #436 by adding __iter__() support to both LayoutElements and Elements classes.

Changes:

• Implemented __iter__() method in:

  • LayoutElements (delegates to .iter_elements())
  • Elements (delegates to .iter_elements())

• Enables native Python-style iteration:

  for el in layout_elements:
      ...

• Added a minimal unit test to confirm LayoutElements can be iterated over directly.

Test Coverage:

• Added: test_layout_elements_iter_support to validate the new behavior.