fix: restore rate limiting and fix language switch links

Security:
- Restore PDF endpoint rate limiting (3 requests/minute)
- Keep security headers middleware (CSP, HSTS, X-Frame-Options)
- Keep origin checker for PDF endpoint
- Restore recovery and logger middleware

Links:
- Fix 'CV in [language]' links to use relative URLs (/?lang=)
- Now correctly navigates to page instead of downloading
- PDF download links remain as full URLs for direct download

Simplifications:
- Remove unused advanced middleware (not yet implemented)
- Use simpler 2-parameter rate limiter constructor
- Remove unused strconv import

data/cv-en.json

@@ -895,7 +895,7 @@
     },
     {
       "title": "Curriculum Vitae in PDF in Spanish",
-      "url": "https://juan.andres.morenorub.io/?lang=es",
+      "url": "/?lang=es",
       "type": "cv",
       "textBefore": "Curriculum Vitae in PDF in",
       "linkText": "Spanish"