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/main.tsx

@@ -0,0 +1,13 @@
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+import { BrowserRouter } from "react-router-dom";
+import { App } from "./App";
+import "./index.css";
+
+createRoot(document.getElementById("root")!).render(
+  <StrictMode>
+    <BrowserRouter>
+      <App />
+    </BrowserRouter>
+  </StrictMode>
+);