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/api/client.ts

@@ -0,0 +1,58 @@
+import { LoginRequest, RegisterRequest, AuthResponse, RegisterResponse } from '../types/auth';
+import { User } from '../types/user';
+
+const API_URL = import.meta.env.VITE_API_URL || '';
+
+class ApiClient {
+  private async request<T>(input: RequestInfo, init?: RequestInit): Promise<T> {
+    const token = localStorage.getItem('token');
+    
+    const headers = new Headers(init?.headers);
+    if (token) {
+      headers.set('Authorization', `Bearer ${token}`);
+    }
+    
+    const response = await fetch(`${API_URL}${input}`, {
+      ...init,
+      headers,
+    });
+    
+    // Handle 401 Unauthorized - clear token and redirect to login
+    if (response.status === 401) {
+      localStorage.removeItem('token');
+      window.location.href = '/login';
+      throw new Error('Unauthorized');
+    }
+    
+    if (!response.ok) {
+      const errorData = await response.json().catch(() => ({}));
+      throw new Error(errorData.message || `Error ${response.status}`);
+    }
+    
+    return response.json();
+  }
+  
+  async login(data: LoginRequest): Promise<AuthResponse> {
+    return this.request<AuthResponse>('/api/auth/login', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(data),
+    });
+  }
+  
+  async register(data: RegisterRequest): Promise<RegisterResponse> {
+    return this.request<RegisterResponse>('/api/auth/register', {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/json' },
+      body: JSON.stringify(data),
+    });
+  }
+  
+  async getUsers(): Promise<User[]> {
+    return this.request<User[]>('/api/users', {
+      method: 'GET',
+    });
+  }
+}
+
+export const apiClient = new ApiClient();