feat: rewrite ApiService for registration API, remove ScanRecord model

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

lib/services/api_service.dart

@@ -1,29 +1,78 @@
 import 'dart:convert';
 import 'package:http/http.dart' as http;
 
+/// Result of a registration API call.
+class RegistrationResult {
+  final bool success;
+  final bool isDuplicate;
+  final String? errorMessage;
+  final Map<String, dynamic>? duplicateInfo;
+
+  RegistrationResult({
+    required this.success,
+    this.isDuplicate = false,
+    this.errorMessage,
+    this.duplicateInfo,
+  });
+
+  factory RegistrationResult.ok() =>
+      RegistrationResult(success: true);
+
+  factory RegistrationResult.duplicate(Map<String, dynamic> info) =>
+      RegistrationResult(success: false, isDuplicate: true, duplicateInfo: info);
+
+  factory RegistrationResult.error(String message) =>
+      RegistrationResult(success: false, errorMessage: message);
+}
+
 class ApiService {
   final http.Client _client;
+  final Duration timeout;
 
-  ApiService({http.Client? client}) : _client = client ?? http.Client();
+  ApiService({http.Client? client, this.timeout = const Duration(seconds: 5)})
+      : _client = client ?? http.Client();
 
-  Future<bool> sendScanData(
-    String url, {
-    required String barcode,
-    required String codeType,
+  /// Submit a shelf registration (上架登记).
+  Future<RegistrationResult> registerLocation({
+    required String baseUrl,
+    required String zongpaiNo,
+    required String locationCode,
   }) async {
+    final uri = Uri.parse('$baseUrl/CargoTrace/location');
     try {
       final response = await _client
           .post(
-            Uri.parse(url),
+            uri,
             headers: {'Content-Type': 'application/json'},
             body: jsonEncode({
-              'barcode': barcode,
-              'code_type': codeType,
-              'timestamp': DateTime.now().toUtc().toIso8601String(),
+              'zongpai_no': zongpaiNo,
+              'location_code': locationCode,
             }),
           )
-          .timeout(const Duration(seconds: 5));
-      return response.statusCode >= 200 && response.statusCode < 300;
+          .timeout(timeout);
+
+      switch (response.statusCode) {
+        case 200:
+          return RegistrationResult.ok();
+        case 409:
+          final body = jsonDecode(response.body) as Map<String, dynamic>;
+          return RegistrationResult.duplicate(body);
+        default:
+          final body = jsonDecode(response.body) as Map<String, dynamic>;
+          final msg = body['error'] ?? body['message'] ?? 'Unknown error (${response.statusCode})';
+          return RegistrationResult.error(msg.toString());
+      }
+    } catch (e) {
+      return RegistrationResult.error('网络异常，请检查网络连接');
+    }
+  }
+
+  /// Test connectivity by making a HEAD request to the base URL.
+  Future<bool> testConnection(String baseUrl) async {
+    try {
+      final uri = Uri.parse(baseUrl);
+      final response = await _client.head(uri).timeout(timeout);
+      return response.statusCode < 500;
     } catch (_) {
       return false;
     }