feat: add barcode scanner for medicine lookup

frontend-mobile/app/(tabs)/index.tsx

@@ -1,15 +1,18 @@
 import React, { useState, useEffect } from 'react';
-import { View, FlatList, StyleSheet, Text } from 'react-native';
+import { View, FlatList, StyleSheet, Text, TouchableOpacity } from 'react-native';
+import { Ionicons } from '@expo/vector-icons';
+import { useRouter } from 'expo-router';
 import { SearchBar } from '../../components/SearchBar';
 import { MedicineCard } from '../../components/MedicineCard';
 import { LoadingSpinner } from '../../components/LoadingSpinner';
 import { useDebounce } from '../../hooks/useDebounce';
 import { searchMedicines } from '../../services/medicines';
-import { colors, spacing } from '../../constants/theme';
+import { colors, spacing, borderRadius } from '../../constants/theme';
 import { Medicine } from '../../types';
 import { config } from '../../constants/config';
 
 export default function HomeScreen() {
+  const router = useRouter();
   const [query, setQuery] = useState('');
   const [results, setResults] = useState<Medicine[]>([]);
   const [isLoading, setIsLoading] = useState(false);
@@ -46,11 +49,19 @@ export default function HomeScreen() {
 
   return (
     <View style={styles.container}>
-      <SearchBar
-        onSearch={handleSearch}
-        value={query}
-        onChangeText={setQuery}
-      />
+      <View style={styles.searchContainer}>
+        <SearchBar
+          onSearch={handleSearch}
+          value={query}
+          onChangeText={setQuery}
+        />
+        <TouchableOpacity 
+          style={styles.scannerButton}
+          onPress={() => router.push('/scanner')}
+        >
+          <Ionicons name="scan" size={24} color={colors.primary} />
+        </TouchableOpacity>
+      </View>
       
       {isLoading && <LoadingSpinner message="Buscando medicamentos..." />}
       
@@ -82,6 +93,16 @@ const styles = StyleSheet.create({
     flex: 1,
     backgroundColor: colors.background,
   },
+  searchContainer: {
+    flexDirection: 'row',
+    alignItems: 'center',
+  },
+  scannerButton: {
+    marginRight: spacing.md,
+    padding: spacing.sm,
+    backgroundColor: colors.card,
+    borderRadius: borderRadius.md,
+  },
   list: {
     paddingBottom: spacing.xl,
   },