refactor: split app into modular src architecture

src/components/BottomTab.js

@@ -0,0 +1,28 @@
+import React from 'react';
+import { Pressable, Text, View } from 'react-native';
+import { styles } from '../styles';
+
+export default function BottomTab({ current, onChange }) {
+  const tabs = [
+    { key: 'trips', label: 'Trips' },
+    { key: 'items', label: 'Items' },
+    { key: 'checkup', label: 'Check-Up' },
+    { key: 'history', label: 'History' },
+  ];
+
+  return (
+    <View style={styles.tabBarWrap}>
+      <View style={styles.tabBar}>
+        {tabs.map((tab) => {
+          const active = current === tab.key;
+          return (
+            <Pressable key={tab.key} onPress={() => onChange(tab.key)} style={styles.tabItem}>
+              <View style={[styles.tabDot, active && styles.tabDotActive]} />
+              <Text style={[styles.tabLabel, active && styles.tabLabelActive]}>{tab.label}</Text>
+            </Pressable>
+          );
+        })}
+      </View>
+    </View>
+  );
+}