feat: comprehensive WCAG 2.1 AA accessibility audit

- Add aria-labels to menu action buttons (PDF, Print, Contact)
- Add aria-labelledby to toggle checkboxes (desktop + mobile)
- Add -webkit-user-select prefix for Safari compatibility
- Add DynamicCacheControl middleware for HTML pages
- Add accessibility test suite (60-accessibility.test.mjs)
- Add comprehensive accessibility documentation (21-ACCESSIBILITY.md)
- Update Modern Web Techniques doc to mark audit complete

internal/routes/routes.go

@@ -56,11 +56,13 @@ func Setup(cvHandler *handlers.CVHandler, healthHandler *handlers.HealthHandler)
 	mux.Handle("/static/", middleware.CacheControl(staticHandler))
 
 	// Apply comprehensive middleware chain
-	// Order: Recovery → Logger → SecurityHeaders → Preferences → Mux
+	// Order: Recovery → Logger → SecurityHeaders → DynamicCacheControl → Preferences → Mux
 	handler := middleware.Recovery(
 		middleware.Logger(
 			middleware.SecurityHeaders(
-				middleware.PreferencesMiddleware(mux),
+				middleware.DynamicCacheControl(
+					middleware.PreferencesMiddleware(mux),
+				),
 			),
 		),
 	)