feat(message): add pinned conversations sorting and unified timeline

Sort conversation list with pinned items first, then by updated_at timestamp.
Also fixes timestamp text alignment by adding lineHeight, textAlignVertical,
and includeFontPadding properties for consistent vertical centering.

src/screens/message/components/ConversationListRow.tsx

@@ -265,6 +265,9 @@ function createConversationRowStyles(colors: AppColors) {
       color: '#FFFFFF',
       fontSize: 12,
       fontWeight: '700',
+      lineHeight: 20,
+      textAlignVertical: 'center',
+      includeFontPadding: false,
     },
   });
 }