fix(models): accept capacity categories without names

[WilliamK112]

OFSC can return capacity categories without a name key. The required string currently rejects the whole list page or a successful PUT reply. Make CapacityCategory.name optional with a default of None so those records can be read and updated.

Regression coverage includes missing, null, and present names, public single-item and paginated reads, and deactivating a nameless category with name omitted from its write body.

Fixes #189.

Validation with Python 3.13:

• All 453 mocked tests pass, with 8 skipped. Five new cases failed before the model change; the named-category control already passed.
• Full Ruff check, Ruff format check, and diff whitespace checks pass.