feat(compliance): add GDPR/RODO compliant cookie consent banner

Implemented cookie consent banner to comply with EU regulations (GDPR/RODO).
The banner appears on first visit and stores user preference in localStorage.

Features:
- Non-intrusive bottom banner with clear messaging
- Accept/Decline options for user choice
- Link to privacy policy in About Us page
- Responsive design for mobile and desktop
- Auto-dismisses after consent with 1s delay on first show
- High z-index to stay above all content

Also added comprehensive Privacy & Cookies section to About Us page
explaining:
- What cookies we use (essential, analytics, preferences)
- How we handle user data
- GDPR/RODO compliance statements
- Contact information for privacy questions

Changes:
- Created CookieConsent component with modern UI
- Integrated banner into App.jsx
- Updated about-us.md with privacy policy section

frontend/src/App.jsx

@@ -26,6 +26,7 @@ import HowItWorksPage from './pages/HowItWorksPage';
 import NotFoundPage from './pages/NotFoundPage';
 import VerificationBanner from './components/common/VerificationBanner';
 import InstallPWA from './components/pwa/InstallPWA';
+import CookieConsent from './components/common/CookieConsent';
 
 // Protected Route Component with Verification Banner
 const ProtectedRoute = ({ children }) => {
@@ -77,6 +78,9 @@ function App() {
         {/* PWA Install Prompt */}
         <InstallPWA />
 
+        {/* Cookie Consent Banner */}
+        <CookieConsent />
+
         {/* Toast Notifications */}
         <Toaster
           position="top-right"