feat: Enhance agent selection and conversation handling

- Added functionality to select agents in the Navigation component, allowing users to reset conversations and set the selected agent.
- Updated the MessageInput component to conditionally show source and tool buttons based on the selected agent.
- Modified the Conversation component to handle agent-specific queries and manage file uploads.
- Improved conversation fetching logic to include agent IDs and handle attachments.
- Introduced new types for conversation summaries and results to streamline API responses.
- Refactored Redux slices to manage selected agent state and improve overall state management.
- Enhanced error handling and loading states across components for better user experience.

frontend/src/conversation/conversationModels.ts

@@ -51,5 +51,6 @@ export interface RetrievalPayload {
   token_limit: number;
   isNoneDoc: boolean;
   index?: number;
+  agent_id?: string;
   attachments?: string[];
 }