Add iPhone dictation guidance

src/screens/ChatScreen.tsx

@@ -1,6 +1,6 @@
 import type { NativeStackScreenProps } from '@react-navigation/native-stack';
 import { useState } from 'react';
-import { FlatList, KeyboardAvoidingView, Platform, StyleSheet, TextInput, View } from 'react-native';
+import { FlatList, KeyboardAvoidingView, Platform, StyleSheet, Text, TextInput, View } from 'react-native';
 import { SafeAreaView } from 'react-native-safe-area-context';
 
 import { ChatBubble, type ChatMessage } from '../components/ChatBubble';
@@ -59,11 +59,14 @@ export function ChatScreen({ route }: ChatScreenProps) {
           <TextInput
             multiline
             onChangeText={setInput}
-            placeholder="Write an English sentence..."
+            placeholder="Write or dictate an English sentence..."
             placeholderTextColor={colors.textSecondary}
             style={styles.input}
             value={input}
           />
+          <Text style={styles.dictationHint}>
+            Tip: tap this field and use the iPhone keyboard microphone to dictate your sentence.
+          </Text>
           <View style={styles.actionRow}>
             <View style={styles.actionItem}>
               <PrimaryButton label={isSending ? 'Thinking...' : 'Send'} onPress={sendMessage} />
@@ -123,4 +126,9 @@ const styles = StyleSheet.create({
     padding: 14,
     textAlignVertical: 'top',
   },
+  dictationHint: {
+    color: colors.textSecondary,
+    fontSize: 12,
+    lineHeight: 17,
+  },
 });