Fix accessibility violations: color contrast, aside nesting

- Improve text contrast from #666/#888/#999 to #555/#6b6b6b across site (WCAG AA)
- Fix aside nesting in all 10 blog articles (aside→div in related-articles)
- Fix aside nesting in quote sidebar
- Update CRO enhancement CSS/JS inline colors

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

assets/css/cro-enhancements.css

@@ -71,7 +71,7 @@
     background: #00b359;
 }
 .sticky-cta-bar .close-bar {
-    color: #888;
+    color: #6b6b6b;
     cursor: pointer;
     padding: 5px;
     font-size: 1.2em;
@@ -113,7 +113,7 @@
     right: 20px;
     font-size: 1.5em;
     cursor: pointer;
-    color: #999;
+    color: #6b6b6b;
 }
 .exit-popup h3 {
     margin: 0 0 15px 0;
@@ -121,7 +121,7 @@
     font-size: 1.5em;
 }
 .exit-popup p {
-    color: #666;
+    color: #555;
     margin-bottom: 25px;
     line-height: 1.6;
 }
@@ -165,7 +165,7 @@
 .exit-popup .no-thanks {
     display: block;
     margin-top: 15px;
-    color: #999;
+    color: #6b6b6b;
     font-size: 0.9em;
     cursor: pointer;
 }

assets/css/main.css

@@ -4653,7 +4653,7 @@ body { font-size: 17px; }
 
 .bio-role {
     font-size: 0.95rem;
-    color: #666;
+    color: #555;
     margin: 0 0 12px 0;
     font-weight: 500;
 }