feat(skills): consolidate skill-related models and update imports

backend/tests/test_organizations_service.py

@@ -17,7 +17,7 @@ from app.models.organization_invite_board_access import OrganizationInviteBoardA
 from app.models.organization_invites import OrganizationInvite
 from app.models.organization_members import OrganizationMember
 from app.models.organizations import Organization
-from app.models.skill_packs import SkillPack
+from app.models.skills import SkillPack
 from app.models.users import User
 from app.schemas.organizations import OrganizationBoardAccessSpec, OrganizationMemberAccessUpdate
 from app.services import organizations

backend/tests/test_skills_marketplace_api.py

@@ -23,12 +23,10 @@ from app.api.skills_marketplace import (
 )
 from app.api.skills_marketplace import router as skills_marketplace_router
 from app.db.session import get_session
-from app.models.gateway_installed_skills import GatewayInstalledSkill
 from app.models.gateways import Gateway
-from app.models.marketplace_skills import MarketplaceSkill
 from app.models.organization_members import OrganizationMember
 from app.models.organizations import Organization
-from app.models.skill_packs import SkillPack
+from app.models.skills import GatewayInstalledSkill, MarketplaceSkill, SkillPack
 from app.services.organizations import OrganizationContext