feat(mobile): Netralax-branded Chats placeholder screen

apps/mobile/app/(app)/chats.tsx

@@ -1,18 +1,25 @@
-// Chats list placeholder.
-// Milestone 1 TODO: render list of conversations, decrypt last-message preview,
-// navigate to a conversation screen on tap.
-
 import { StyleSheet, Text, View } from 'react-native';
 
+// Phase 0 stand-in for the conversation list. Confirms the authenticated
+// route group (`(app)`) mounts without error after a navigation from
+// Landing. Phase 1 replaces this with the real chat list.
 export default function Chats() {
   return (
     <View style={styles.container}>
-      <Text style={styles.text}>Chats — placeholder</Text>
+      <Text style={styles.title}>Netralax</Text>
+      <Text style={styles.subtitle}>Chats — coming soon (Phase 1)</Text>
     </View>
   );
 }
 
 const styles = StyleSheet.create({
-  container: { flex: 1, alignItems: 'center', justifyContent: 'center', backgroundColor: '#0b0b0f' },
-  text: { color: '#fff' },
+  container: {
+    flex: 1,
+    alignItems: 'center',
+    justifyContent: 'center',
+    backgroundColor: '#0b0b0f',
+    padding: 24,
+  },
+  title: { color: '#fff', fontSize: 28, fontWeight: '600' },
+  subtitle: { color: '#9ca3af', marginTop: 8, textAlign: 'center' },
 });