feat: implement user profile management (Fase 2)

- Add useProfile hook for managing user data
- Add Profile page to view/edit user information
- Add Settings layout with sidebar navigation
- Add Settings pages: Profile, Password, Notifications, Account
- Add user dropdown menu in Header with Profile/Settings links
- Add protected routes for /settings/* pages
- Implement profile update and password change functionality

Completes Fase 2 of frontend missing features analysis from todo.md

frontend/src/App.tsx

@@ -1,5 +1,5 @@
 import { Suspense, lazy } from 'react';
-import { BrowserRouter, Routes, Route } from 'react-router-dom';
+import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom';
 import { QueryProvider } from './providers/QueryProvider';
 import { ThemeProvider } from './providers/ThemeProvider';
 import { AuthProvider } from './contexts/AuthContext';
@@ -22,6 +22,11 @@ const Login = lazy(() => import('./pages/Login').then(m => ({ default: m.Login }
 const Register = lazy(() => import('./pages/Register').then(m => ({ default: m.Register })));
 const ForgotPassword = lazy(() => import('./pages/ForgotPassword').then(m => ({ default: m.ForgotPassword })));
 const ResetPassword = lazy(() => import('./pages/ResetPassword').then(m => ({ default: m.ResetPassword })));
+const SettingsLayout = lazy(() => import('./pages/settings/SettingsLayout').then(m => ({ default: m.SettingsLayout })));
+const SettingsProfile = lazy(() => import('./pages/settings/SettingsProfile').then(m => ({ default: m.SettingsProfile })));
+const SettingsPassword = lazy(() => import('./pages/settings/SettingsPassword').then(m => ({ default: m.SettingsPassword })));
+const SettingsNotifications = lazy(() => import('./pages/settings/SettingsNotifications').then(m => ({ default: m.SettingsNotifications })));
+const SettingsAccount = lazy(() => import('./pages/settings/SettingsAccount').then(m => ({ default: m.SettingsAccount })));
 const ApiKeys = lazy(() => import('./pages/ApiKeys').then(m => ({ default: m.ApiKeys })));
 const AnalyticsDashboard = lazy(() => import('./pages/AnalyticsDashboard').then(m => ({ default: m.AnalyticsDashboard })));
 const NotFound = lazy(() => import('./pages/NotFound').then(m => ({ default: m.NotFound })));
@@ -75,16 +80,30 @@ function App() {
               <Route path="/forgot-password" element={<ForgotPassword />} />
               <Route path="/reset-password" element={<ResetPassword />} />
               
-              {/* Protected routes with layout */}
-              <Route path="/" element={<ProtectedLayout />}>
-                <Route index element={<Dashboard />} />
-                <Route path="scenarios" element={<ScenariosPage />} />
-                <Route path="scenarios/:id" element={<ScenarioDetail />} />
-                <Route path="scenarios/:id/reports" element={<Reports />} />
-                <Route path="compare" element={<Compare />} />
-                <Route path="settings/api-keys" element={<ApiKeys />} />
-                <Route path="analytics" element={<AnalyticsDashboard />} />
-              </Route>
+            {/* Protected routes with layout */}
+            <Route path="/" element={<ProtectedLayout />}>
+              <Route index element={<Dashboard />} />
+              <Route path="scenarios" element={<ScenariosPage />} />
+              <Route path="scenarios/:id" element={<ScenarioDetail />} />
+              <Route path="scenarios/:id/reports" element={<Reports />} />
+              <Route path="compare" element={<Compare />} />
+              <Route
+                path="settings"
+                element={
+                  <SettingsLayout>
+                    <Routes>
+                      <Route index element={<Navigate to="/settings/profile" replace />} />
+                      <Route path="profile" element={<SettingsProfile />} />
+                      <Route path="password" element={<SettingsPassword />} />
+                      <Route path="notifications" element={<SettingsNotifications />} />
+                      <Route path="account" element={<SettingsAccount />} />
+                      <Route path="api-keys" element={<ApiKeys />} />
+                    </Routes>
+                  </SettingsLayout>
+                }
+              />
+              <Route path="analytics" element={<AnalyticsDashboard />} />
+            </Route>
               
               {/* 404 */}
               <Route path="*" element={<NotFound />} />