Skills now link to services, not categories

You can now link each skill directly to the services it supports, instead of filing it under a separate category.

• The skills page no longer has a categories tab — each skill’s card shows the services it supports instead.
• When you create or edit a skill, you pick one or more services it supports instead of a category.
• You can filter the skills list by service.

Every skill needs at least one linked service, so the catalogue always shows what each skill is actually for.