fix: improve contrast in CommentList avatar for WCAG compliance

- Change color from 'white' to '#ffffff' for better specificity
- Use darker gradient colors (#2563eb, #7c3aed) for better contrast
- Update dark mode gradient to even darker shades (#1e40af, #6d28d9)

Author: kanishkagarwal6101

src/components/EductionPortal/Tasks/CommentList.module.css

@@ -136,18 +136,18 @@
   width: 40px;
   height: 40px;
   border-radius: 50%;
-  background: linear-gradient(135deg, #3b82f6, #8b5cf6);
+  background: linear-gradient(135deg, #2563eb, #7c3aed);
   display: flex;
   align-items: center;
   justify-content: center;
-  color: white;
+  color: #ffffff;
   font-weight: 600;
   font-size: 0.875rem;
   flex-shrink: 0;
 }
 
 .avatarDark {
-  background: linear-gradient(135deg, #2563eb, #7c3aed);
+  background: linear-gradient(135deg, #1e40af, #6d28d9);
 }
 
 .authorDetails {
@@ -253,4 +253,4 @@
 
 .deleteButtonDark:hover {
   background-color: #7f1d1d;
-}
+}