Implement factorization for ideals of maximal number field orders

[cxzhong]

This adds factor() to number field order ideals when the order is maximal.

The implementation reuses the existing fractional ideal factorization and changes the resulting factors back to the original order ideal monoid. This keeps every returned factor in the same maximal order as the input ideal. Factorization of non-maximal order ideals remains explicitly unsupported, and zero ideal factorization raises the standard arithmetic error.

The doctests cover reconstruction of the input ideal, factor parents, caching, the unit and zero ideals, non-maximal orders, ramified/inert/split primes in a quadratic field, and relative number fields. The number field order tutorial is updated for the explicit non-maximal-order error.

Fixes #42677.

📝 Checklist

• The title is concise and informative.
• The description explains in detail what this PR is about.
• I have linked a relevant issue or discussion.
• I have created tests covering the changes.
• I have updated the documentation and checked the relevant documentation doctests.

⌛ Dependencies

None.

[github-actions]

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