feat(authentication): implement frontend authentication system

- Created auth and user types (T10)
- Implemented API client with token handling (T11)
- Built AuthContext with JWT decoding (T12)
- Added ProtectedRoute component (T13)
- Created LoginPage, RegisterPage, DashboardPage (T14-T16)
- Updated App.tsx with routing and auth provider (T17)
- Added Dockerfile, nginx.conf for frontend deployment (T18-T19)
- Updated docker-compose.yml to include frontend service (T20)
- Updated .gitignore to exclude frontend build artifacts (T21)
- Removed unused App.css (T22)

Refs #2

Frontend/src/main.tsx

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