shokollm
7c17bff110
feat: add category service layer methods
Service layer for category feature (Issue #86):
Category Management:
- add_category() - Create category (admin only, validates slug format)
- delete_category() - Soft delete category (admin only)
- list_categories() - List active categories
- get_category() - Get category by slug
Category-to-Bounty Association:
- add_category_to_bounty() - Add category to bounty (admin only)
- remove_category_from_bounty() - Remove category from bounty (admin only)
- update_bounty_categories() - Replace all categories on bounty (admin only)
All methods properly validate permissions, slug format, and existence.
Soft delete preserves category data for bounties that reference it.