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;
+    }
+  }
+}