fix(news): use onSurface for article titles instead of primary

Purple-on-black was eye-catching but hard to read. Switch title text
to onSurface for contrast; keep the underline in primary at 70% alpha
as the "this is a link" signal.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/widgets/news_card.dart

@@ -113,16 +113,20 @@ class NewsCard extends StatelessWidget {
               ],
             ),
             const SizedBox(height: 4),
-            // Title — tappable if URL present
+            // Title — tappable if URL present. Text stays in onSurface for
+            // contrast; the primary-colored underline carries the "this is a
+            // link" signal without tanking readability.
             GestureDetector(
               onTap: item.url.isNotEmpty ? _openUrl : null,
               child: Text(
                 item.title,
-                style: textTheme.bodyMedium?.copyWith(
+                style: textTheme.titleSmall?.copyWith(
                   fontWeight: FontWeight.w600,
-                  color: item.url.isNotEmpty ? scheme.primary : scheme.onSurface,
+                  color: scheme.onSurface,
+                  height: 1.3,
                   decoration: item.url.isNotEmpty ? TextDecoration.underline : null,
-                  decorationColor: scheme.primary,
+                  decorationColor: scheme.primary.withValues(alpha: 0.7),
+                  decorationThickness: 1.5,
                 ),
               ),
             ),