chore(mobile/login): drop dead brandDot/title styles from old design

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mobile/src/screens/LoginScreen.tsx

@@ -156,25 +156,6 @@ const styles = StyleSheet.create({
   scroll: { flexGrow: 1, justifyContent: 'center', padding: 24 },
 
   brandBlock: { marginBottom: 28, alignItems: 'flex-start' },
-  brandDot: {
-    width: 12,
-    height: 12,
-    borderRadius: 6,
-    backgroundColor: theme.accent,
-    marginBottom: 14,
-    shadowColor: theme.accent,
-    shadowOffset: { width: 0, height: 0 },
-    shadowOpacity: 0.8,
-    shadowRadius: 10,
-    elevation: 6,
-  },
-  title: {
-    color: theme.fg,
-    fontSize: 44,
-    fontWeight: '800',
-    marginBottom: 4,
-    letterSpacing: -1.5,
-  },
   subtitle: {
     color: theme.muted,
     fontSize: 14,