feat: add ApiService for HTTP POST

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/services/api_service.dart

@@ -0,0 +1,31 @@
+import 'dart:convert';
+import 'package:http/http.dart' as http;
+
+class ApiService {
+  final http.Client _client;
+
+  ApiService({http.Client? client}) : _client = client ?? http.Client();
+
+  Future<bool> sendScanData(
+    String url, {
+    required String barcode,
+    required String codeType,
+  }) async {
+    try {
+      final response = await _client
+          .post(
+            Uri.parse(url),
+            headers: {'Content-Type': 'application/json'},
+            body: jsonEncode({
+              'barcode': barcode,
+              'code_type': codeType,
+              'timestamp': DateTime.now().toUtc().toIso8601String(),
+            }),
+          )
+          .timeout(const Duration(seconds: 5));
+      return response.statusCode >= 200 && response.statusCode < 300;
+    } catch (_) {
+      return false;
+    }
+  }
+}

test/services/api_service_test.dart

@@ -0,0 +1,34 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart';
+import 'package:pad_scanner/services/api_service.dart';
+
+void main() {
+  group('ApiService', () {
+    test('sendScanData returns true on 200', () async {
+      final client = MockClient((request) async {
+        return http.Response('{"status":"ok"}', 200);
+      });
+      final service = ApiService(client: client);
+      final result = await service.sendScanData(
+        'http://localhost:8000/scan',
+        barcode: '123456',
+        codeType: 'CODE128',
+      );
+      expect(result, isTrue);
+    });
+
+    test('sendScanData returns false on error', () async {
+      final client = MockClient((request) async {
+        return http.Response('error', 500);
+      });
+      final service = ApiService(client: client);
+      final result = await service.sendScanData(
+        'http://localhost:8000/scan',
+        barcode: '123456',
+        codeType: 'CODE128',
+      );
+      expect(result, isFalse);
+    });
+  });
+}