feat(frontend): Task 14 - Vite React TypeScript scaffolding with Tailwind CSS

Sets up the frontend SPA foundation: Vite+React+TS project at frontend/,
configures Tailwind CSS v4 via @tailwindcss/vite, dev proxy to port 4000,
and implements the API client (JWT auth, auto-redirect on 401).

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

display/frontend/index.html

@@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="en">
+  <head>
+    <meta charset="UTF-8" />
+    <link rel="icon" type="image/svg+xml" href="/favicon.svg" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <title>frontend</title>
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>