feat(analytics): integrate Google Analytics 4 with GDPR compliance

Prepared the application for Google Analytics 4 tracking with full
GDPR/RODO compliance. GA only loads after user explicitly accepts cookies.

Features:
- Automatic page view tracking on route changes
- Custom event tracking for key user actions
- Privacy-first: GA loads only after cookie consent
- Easy configuration via environment variable
- Comprehensive tracking utilities for common events

Implementation:
- Created analytics.js with GA initialization and event tracking functions
- Created usePageTracking hook for automatic page view tracking
- Integrated GA into App.jsx with AnalyticsWrapper component
- Updated CookieConsent to initialize GA after user consent
- Added VITE_GA_MEASUREMENT_ID to .env.example

Custom events tracked:
- login, sign_up (authentication)
- match_request, match_accepted (matching)
- webrtc_connection, file_transfer (WebRTC)
- event_join, recording_suggestion (events/recording)
- search (search functionality)

Setup:
1. Add VITE_GA_MEASUREMENT_ID=G-XXXXXXXXXX to .env
2. Restart frontend container
3. GA will auto-load after user accepts cookies

Documentation:
- Created comprehensive setup guide in docs/GOOGLE_ANALYTICS_SETUP.md
- Includes troubleshooting, debugging tips, and usage examples

frontend/src/components/common/CookieConsent.jsx

@@ -1,5 +1,6 @@
 import { useState, useEffect } from 'react';
 import { Cookie, X } from 'lucide-react';
+import { initGA } from '../../utils/analytics';
 
 /**
  * GDPR/RODO compliant cookie consent banner
@@ -20,6 +21,12 @@ const CookieConsent = () => {
   const handleAccept = () => {
     localStorage.setItem('cookieConsent', 'accepted');
     setIsVisible(false);
+
+    // Initialize Google Analytics after consent
+    const measurementId = import.meta.env.VITE_GA_MEASUREMENT_ID;
+    if (measurementId) {
+      setTimeout(() => initGA(measurementId), 500);
+    }
   };
 
   const handleDecline = () => {