refactor: remove knowledge base references from AI agent model and related services

- Removed KnowledgeIDs from CreateAIAgentRequest and AIAgentResponse.
- Updated buildAIAgentResponseWithLocale to eliminate knowledge base name retrieval.
- Refactored AI agent repository and service to remove knowledge base handling.
- Adjusted dashboard service to no longer track AI agents without knowledge bases.
- Modified knowledge base service to check for workflow references instead of AI agent references.
- Updated frontend components to remove knowledge base selection and display.
- Enhanced workflow validation to ensure knowledge retrieve nodes have associated knowledge bases.

internal/handlers/dashboard/ai_agent_handler.go

@@ -182,9 +182,7 @@ func buildAIAgentResponseWithLocale(item *models.AIAgent, locale string) respons
 		FallbackMode:        item.FallbackMode,
 		FallbackModeName:    enums.GetAIAgentFallbackModeLabel(item.FallbackMode),
 		FallbackMessage:     item.FallbackMessage,
-		KnowledgeIDs:        utils.SplitInt64s(item.KnowledgeIDs),
 		SkillIDs:            utils.SplitInt64s(item.SkillIDs),
-		KnowledgeBaseNames:  make([]string, 0),
 		Skills:              make([]response.AIAgentSkillResponse, 0),
 		Teams:               make([]response.AIAgentTeamResponse, 0),
 		DirectTools:         make([]response.AIAgentMCPToolResponse, 0),
@@ -209,11 +207,6 @@ func buildAIAgentResponseWithLocale(item *models.AIAgent, locale string) respons
 			})
 		}
 	}
-	for _, id := range ret.KnowledgeIDs {
-		if knowledgeBase := services.KnowledgeBaseService.Get(id); knowledgeBase != nil {
-			ret.KnowledgeBaseNames = append(ret.KnowledgeBaseNames, knowledgeBase.Name)
-		}
-	}
 	for _, id := range ret.SkillIDs {
 		if skill := services.SkillDefinitionService.Get(id); skill != nil {
 			ret.Skills = append(ret.Skills, response.AIAgentSkillResponse{