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, 18 insertions, 0 deletions

diff --git a/vite.config.ts b/vite.config.ts
new file mode 100644
index 0000000..757a0af
--- /dev/null
+++ b/vite.config.ts
@@ -0,0 +1,18 @@
+import react from "@vitejs/plugin-react";
+import { defineConfig } from "vite";
+
+export default defineConfig({
+	plugins: [react()],
+	root: ".",
+	build: {
+		outDir: "dist/client",
+	},
+	server: {
+		proxy: {
+			"/api": {
+				target: "http://localhost:3000",
+				changeOrigin: true,
+			},
+		},
+	},
+});