feat(client): initialize React + Vite frontend foundation

Set up the client-side React application with Vite bundler:
- Add React 19 and Vite 7 with the React plugin
- Create index.html entry point and App component
- Configure Vite with API proxy to backend server
- Add client build scripts to package.json
- Update tsconfig for React JSX and DOM types
- Fix TypeScript errors in auth code (JWT_SECRET type narrowing)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

1 files changed, 14 insertions, 0 deletions

diff --git a/src/client/main.tsx b/src/client/main.tsx
new file mode 100644
index 0000000..1e185be
--- /dev/null
+++ b/src/client/main.tsx
@@ -0,0 +1,14 @@
+import { StrictMode } from "react";
+import { createRoot } from "react-dom/client";
+import { App } from "./App";
+
+const rootElement = document.getElementById("root");
+if (!rootElement) {
+	throw new Error("Root element not found");
+}
+
+createRoot(rootElement).render(
+	<StrictMode>
+		<App />
+	</StrictMode>,
+);