Addresses the need for a calendar view.

[Peyman20122]

Hello dear engineer

I added the calendar to the jdatetime library
The checklist is as follows:

· Code follows the project style (PEP8, existing patterns).
· No new external dependencies added.
· Method returns a string, does not print directly.
· Works with both Persian (fa_IR) and English locales.
· Handles edge cases (leap year, month boundaries).