style: adjust fade-in/out effects consistency

- Update fade stop values to 0.02/0.98 from 0.05/0.95 for consistent appearance
- Affected pages: Discover, Headline Details, Saved Filters Bar, Content Collection Decorator

Author: fulleni

lib/discover/view/discover_page.dart

@@ -238,8 +238,8 @@ class _SourceCategoryRowState extends State<_SourceCategoryRow> {
 
                 final stops = <double>[
                   if (showStartFade) 0.0,
-                  if (showStartFade) 0.05 else 0.0,
-                  if (showEndFade) 0.95 else 1.0,
+                  if (showStartFade) 0.02 else 0.0,
+                  if (showEndFade) 0.98 else 1.0,
                   if (showEndFade) 1.0,
                 ];
 

lib/headline-details/view/headline_details_page.dart

@@ -424,8 +424,8 @@ class _HeadlineDetailsPageState extends State<HeadlineDetailsPage> {
 
                 final stops = <double>[
                   if (showStartFade) 0.0,
-                  if (showStartFade) 0.05 else 0.0,
-                  if (showEndFade) 0.95 else 1.0,
+                  if (showStartFade) 0.02 else 0.0,
+                  if (showEndFade) 0.98 else 1.0,
                   if (showEndFade) 1.0,
                 ];
 

lib/headlines-feed/widgets/saved_filters_bar.dart

@@ -264,8 +264,8 @@ class _SavedFiltersBarState extends State<SavedFiltersBar> {
 
             final stops = <double>[
               if (showStartFade) 0.0,
-              if (showStartFade) 0.05 else 0.0,
-              if (showEndFade) 0.95 else 1.0,
+              if (showStartFade) 0.02 else 0.0,
+              if (showEndFade) 0.98 else 1.0,
               if (showEndFade) 1.0,
             ];
 

lib/shared/widgets/feed_decorators/content_collection_decorator_widget.dart

@@ -170,8 +170,8 @@ class _ContentCollectionViewState extends State<_ContentCollectionView> {
 
                 final stops = <double>[
                   if (showStartFade) 0.0,
-                  if (showStartFade) 0.05 else 0.0,
-                  if (showEndFade) 0.95 else 1.0,
+                  if (showStartFade) 0.02 else 0.0,
+                  if (showEndFade) 0.98 else 1.0,
                   if (showEndFade) 1.0,
                 ];