feat: Add visitor analytics, PDF CV generation, country flags, and co…

…mprehensive optimizations

Features:
-  Visitor tracking with IP-based country detection (flag icons)
-  PDF CV generation with QuestPDF
-  Advanced analytics dashboard with charts
-  Email notification system with MailKit
-  Country flag display using flag-icons library

Improvements:
-  Response compression (Brotli/Gzip)
-  Memory caching for better performance
-  Frontend UX enhancements (skeleton loaders)
-  Hardcoded CORS for production reliability
-  Code splitting and bundle optimization
-  SEO improvements (robots.txt, sitemap.xml)

Security:
-  Removed /admin redirect route
-  SQL injection prevention
-  Input validation

Testing:
-  Vitest setup for frontend testing
-  Test infrastructure ready

Docs:
-  Comprehensive bilingual README (TR/EN)
-  Deployment guide
-  Configuration documentation