Fix double /api/ prefix in API endpoint calls

When VITE_API_URL=/api, axios baseURL is already set to /api. However, all endpoint calls included the /api/ prefix, creating double paths like /api/api/auth/login/.

Removed /api/ prefix from 81 API endpoint calls across 22 files:
- src/api/auth.ts - Fixed login, logout, me, refresh, hijack endpoints
- src/api/client.ts - Fixed token refresh endpoint
- src/api/profile.ts - Fixed all profile, email, password, MFA, sessions endpoints
- src/hooks/*.ts - Fixed all remaining API calls (users, appointments, resources, etc)
- src/pages/*.tsx - Fixed signup and email verification endpoints

This ensures API requests use the correct path: /api/auth/login/ instead of /api/api/auth/login/

🤖 Generated with Claude Code

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

frontend/src/components/marketing/Navbar.tsx

@@ -5,6 +5,7 @@ import { Menu, X, Sun, Moon } from 'lucide-react';
 import SmoothScheduleLogo from '../SmoothScheduleLogo';
 import LanguageSelector from '../LanguageSelector';
 import { User } from '../../api/auth';
+import { buildSubdomainUrl } from '../../utils/domain';
 
 interface NavbarProps {
   darkMode: boolean;
@@ -47,10 +48,10 @@ const Navbar: React.FC<NavbarProps> = ({ darkMode, toggleTheme, user }) => {
     const protocol = window.location.protocol;
 
     if (['superuser', 'platform_manager', 'platform_support'].includes(user.role)) {
-      return `${protocol}//platform.lvh.me${port}/`;
+      return buildSubdomainUrl('platform', '/');
     }
     if (user.business_subdomain) {
-      return `${protocol}//${user.business_subdomain}.lvh.me${port}/`;
+      return buildSubdomainUrl(user.business_subdomain, '/');
     }
     return '/login';
   };