Replace the create_fee_type/create_cycle helpers duplicated across 18/8
membership-fee test files with a single shared definition in Mv.Fixtures,
reconciling the divergent local signatures (including the reversed
argument order) into one superset so behavior is unchanged.
- Policy tests: use Fixtures where applicable; create_custom_field() fix in custom_field_value.
- Replace unused actor with _actor, remove unused alias Accounts in policy tests.
- profile_navigation_test: disable Credo for intentional TODO comment.
- Group/MemberGroup/MembershipFeeType/MembershipFeeCycle: HasPermission policy
- normal_user: Group and MembershipFeeCycle create/update/destroy; pages /groups/new, /groups/:slug/edit
- Add policy tests for all four resources
