Initial commit: Expo app with Better Auth integration

- Complete Expo React Native app setup with TypeScript
- Better Auth authentication system integration
- Secure storage implementation for session tokens
- Authentication flow with login/logout functionality
- API client configuration for backend communication
- Responsive UI components with themed styling
- Expo Router navigation setup
- Development configuration and scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

app/(tabs)/_layout.tsx

@@ -0,0 +1,45 @@
+import { Tabs, Redirect } from 'expo-router';
+import React from 'react';
+
+import { HapticTab } from '@/components/haptic-tab';
+import { IconSymbol } from '@/components/ui/icon-symbol';
+import { Colors } from '@/constants/theme';
+import { useColorScheme } from '@/hooks/use-color-scheme';
+import { useAuth } from '@/hooks/use-auth';
+
+export default function TabLayout() {
+  const colorScheme = useColorScheme();
+  const { isAuthenticated, isLoading } = useAuth();
+
+  if (isLoading) {
+    return null;
+  }
+
+  if (!isAuthenticated) {
+    return <Redirect href="/(auth)/login" />;
+  }
+
+  return (
+    <Tabs
+      screenOptions={{
+        tabBarActiveTintColor: Colors[colorScheme ?? 'light'].tint,
+        headerShown: false,
+        tabBarButton: HapticTab,
+      }}>
+      <Tabs.Screen
+        name="index"
+        options={{
+          title: 'Home',
+          tabBarIcon: ({ color }) => <IconSymbol size={28} name="house.fill" color={color} />,
+        }}
+      />
+      <Tabs.Screen
+        name="explore"
+        options={{
+          title: 'Explore',
+          tabBarIcon: ({ color }) => <IconSymbol size={28} name="paperplane.fill" color={color} />,
+        }}
+      />
+    </Tabs>
+  );
+}