feat(web): add login and register pages with auth store

- API client with token refresh interceptor
- Auth API functions (login, register, logout, getMe)
- Auth store with Zustand persistence
- Auth layout with centered card design
- Login page with form validation
- Register page with company and user data
- Environment example file

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/web/stores/auth-store.ts

@@ -0,0 +1,34 @@
+import { create } from 'zustand';
+import { persist } from 'zustand/middleware';
+import type { UserInfo } from '@horux/shared';
+
+interface AuthState {
+  user: UserInfo | null;
+  isAuthenticated: boolean;
+  setUser: (user: UserInfo | null) => void;
+  setTokens: (accessToken: string, refreshToken: string) => void;
+  logout: () => void;
+}
+
+export const useAuthStore = create<AuthState>()(
+  persist(
+    (set) => ({
+      user: null,
+      isAuthenticated: false,
+      setUser: (user) => set({ user, isAuthenticated: !!user }),
+      setTokens: (accessToken, refreshToken) => {
+        localStorage.setItem('accessToken', accessToken);
+        localStorage.setItem('refreshToken', refreshToken);
+      },
+      logout: () => {
+        localStorage.removeItem('accessToken');
+        localStorage.removeItem('refreshToken');
+        set({ user: null, isAuthenticated: false });
+      },
+    }),
+    {
+      name: 'horux-auth',
+      partialize: (state) => ({ user: state.user, isAuthenticated: state.isAuthenticated }),
+    }
+  )
+);