Refactor Assistant navigation and update HomePage button

Updated the AppShell and Sidebar components to streamline navigation for the Assistant section, consolidating assistant-related pages under a single "assistants" key. Removed deprecated assistant sub-items and adjusted the HomePage button to link to the new assistant navigation. Enhanced the AssistantPage with a list view for managing assistants, including mock data for demonstration.

src/components/layout/AppShell.tsx

@@ -6,7 +6,6 @@ import { Topbar } from "./Topbar";
 
 import { HomePage } from "@/components/pages/HomePage";
 import { AssistantPage } from "@/components/pages/AssistantPage";
-import { AssistantWorkflowPage } from "@/components/pages/AssistantWorkflowPage";
 import { ComponentsModelsPage } from "@/components/pages/ComponentsModelsPage";
 import { ComponentsKnowledgePage } from "@/components/pages/ComponentsKnowledgePage";
 import { ComponentsToolsPage } from "@/components/pages/ComponentsToolsPage";
@@ -17,8 +16,7 @@ import { ProfilePage } from "@/components/pages/ProfilePage";
 
 export type NavKey =
   | "home"
-  | "assistant-prompt"
-  | "assistant-workflow"
+  | "assistants"
   | "components-models"
   | "components-knowledge"
   | "components-tools"
@@ -46,10 +44,7 @@ export function AppShell() {
 
         <div className="flex-1 overflow-y-auto px-8 py-10">
           {active === "home" && <HomePage onNavigate={setActive} />}
-
-          {active === "assistant-prompt" && <AssistantPage />}
-          {active === "assistant-workflow" && <AssistantWorkflowPage />}
-
+          {active === "assistants" && <AssistantPage />}
           {active === "components-models" && <ComponentsModelsPage />}
           {active === "components-knowledge" && <ComponentsKnowledgePage />}
           {active === "components-tools" && <ComponentsToolsPage />}