Add React UI with Vite

Dashboard, agents, goals, issues, and projects pages with sidebar
navigation. API client layer, custom hooks, and shared layout
components. Built with Vite and TypeScript.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/components/Layout.tsx

@@ -0,0 +1,13 @@
+import { Outlet } from "react-router-dom";
+import { Sidebar } from "./Sidebar";
+
+export function Layout() {
+  return (
+    <div className="flex h-screen bg-gray-50 text-gray-900">
+      <Sidebar />
+      <main className="flex-1 overflow-auto p-8">
+        <Outlet />
+      </main>
+    </div>
+  );
+}