feat: Expo scaffold + auth screens + core screens (#39-#46, #48)

app/(app)/payments/index.tsx

@@ -0,0 +1,18 @@
+import { View, Text, TouchableOpacity } from 'react-native';
+import { useRouter } from 'expo-router';
+
+export default function PaymentsScreen() {
+  const router = useRouter();
+  return (
+    <View className="flex-1 bg-gray-50 pt-14 px-4">
+      <Text className="text-2xl font-bold text-gray-900 mb-6">Payments</Text>
+      <TouchableOpacity
+        className="bg-primary rounded-2xl p-5 items-center"
+        onPress={() => router.push('/(app)/payments/record')}
+      >
+        <Text className="text-white text-lg font-semibold">💳 Record Payment</Text>
+        <Text className="text-blue-100 text-sm mt-1">Accept cash, GCash, or bank transfer</Text>
+      </TouchableOpacity>
+    </View>
+  );
+}