feat: update references section and fix experience logos in print

References section improvements:
- Remove TwenTIC recommendation letter
- Add Megabanner recommendations with author attribution (David Amorós)
- Update Presentation Letter URL to Domestika profile
- Update Chronological CV link to trigger PDF download modal
- Add 'action' field to Reference struct for custom behaviors

Print layout fixes:
- Show experience company logos in print view (40×40px)
- Remove print media query that was hiding .company-logo elements
- Maintain consistency with other logo types (courses, projects, awards)

Technical changes:
- Add Action field to Reference model with omitempty JSON tag
- Implement conditional rendering for downloadPDF action in template
- Links with action="downloadPDF" now call openPdfModal() function

static/css/logo-toggle.css

@@ -196,12 +196,7 @@
     height: auto;
 }
 
-/* Hide logos in print by default */
-@media print {
-    .company-logo {
-        display: none !important;
-    }
-}
+/* Company logos visible in print - styling controlled by print.css */
 
 /* Mobile responsiveness */
 @media (max-width: 768px) {