Add privacy mode toggle to blur sensitive financial amounts

Eye/EyeOff icon next to theme toggle. Persists in localStorage.
Applies CSS blur to all elements marked with data-sensitive attribute
across Dashboard, Budget, Pensions, Salarios, and Transactions pages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/App.tsx

@@ -1,6 +1,7 @@
 import { BrowserRouter, Routes, Route, Navigate } from 'react-router-dom';
 import { AuthProvider, useAuth } from './AuthContext';
 import { ThemeProvider } from './ThemeContext';
+import { PrivacyProvider } from './PrivacyContext';
 import Layout from './components/Layout';
 import Login from './pages/Login';
 import Dashboard from './pages/Dashboard';
@@ -47,9 +48,11 @@ export default function App() {
   return (
     <BrowserRouter>
       <ThemeProvider>
-        <AuthProvider>
-          <AppRoutes />
-        </AuthProvider>
+        <PrivacyProvider>
+          <AuthProvider>
+            <AppRoutes />
+          </AuthProvider>
+        </PrivacyProvider>
       </ThemeProvider>
     </BrowserRouter>
   );