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/nginx.conf

@@ -0,0 +1,19 @@
+server {
+    listen 80;
+    server_name localhost;
+
+    root /usr/share/nginx/html;
+    index index.html;
+
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+
+    location /api/ {
+        proxy_pass http://backend:5000;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+    }
+}