Add user info header to authentication dropdown

- Created /api/auth/userinfo endpoint to fetch user data from Authentik headers
- Added userInfo state and fetchUserInfo() function to useAuth composable
- Implemented compact user info header in dropdown with avatar, name, and email
- Avatar shows user initials with gradient background
- Styled with glassmorphism design matching app aesthetic

server/api/auth/userinfo.get.ts

@@ -0,0 +1,28 @@
+export default defineEventHandler((event) => {
+  // Authentik forward-auth pasa información del usuario en headers
+  const username = getHeader(event, 'x-authentik-username') || 'Usuario'
+  const email = getHeader(event, 'x-authentik-email') || ''
+  const name = getHeader(event, 'x-authentik-name') || ''
+  const uid = getHeader(event, 'x-authentik-uid') || ''
+
+  // Retornar información del usuario
+  return {
+    username,
+    email,
+    name: name || username, // Usar username si no hay name
+    uid,
+    initials: getInitials(name || username)
+  }
+})
+
+// Helper para obtener iniciales
+function getInitials(name: string): string {
+  if (!name) return '?'
+
+  const parts = name.trim().split(/\s+/)
+  if (parts.length === 1) {
+    return parts[0].substring(0, 2).toUpperCase()
+  }
+
+  return (parts[0][0] + parts[parts.length - 1][0]).toUpperCase()
+}