refactor: split registration page into focused parts

lib/pages/registration/parts/registration_overview_part.dart

@@ -0,0 +1,88 @@
+// ignore_for_file: invalid_use_of_protected_member
+
+part of '../../registration_page.dart';
+
+extension _RegistrationOverviewPart on _RegistrationPageState {
+  /// Find all scanned items that are already on shelf.
+  List<PaichaOverviewItem> _findOnShelfItemsInScanned() {
+    return registration_calculations.findOnShelfItemsInScanned(
+      overview: _overview,
+      zongpaiNos: _zongpaiNos,
+    );
+  }
+
+  /// Find all scanned items that are already transferred.
+  List<PaichaOverviewItem> _findTransferredItemsInScanned() {
+    return registration_calculations.findTransferredItemsInScanned(
+      overview: _overview,
+      zongpaiNos: _zongpaiNos,
+    );
+  }
+
+  /// Whether any scanned item already has a location binding (on_shelf or transferred).
+  bool _hasAnyLocatedInScanned() {
+    return registration_calculations.hasAnyLocatedInScanned(
+      overview: _overview,
+      zongpaiNos: _zongpaiNos,
+    );
+  }
+
+  Future<String?> _baseUrl() async {
+    final configService = AppConfigService();
+    final baseUrl = await configService.getString('api_url') ?? '';
+    if (baseUrl.isEmpty) {
+      return null;
+    }
+    return baseUrl;
+  }
+
+  Future<void> _loadOverview(String zongpaiNo, {bool force = false}) async {
+    if (!force && _overviewZongpaiNo == zongpaiNo && _overview != null) {
+      return;
+    }
+    final requestId = ++_overviewRequestId;
+    setState(() {
+      _overviewZongpaiNo = zongpaiNo;
+      _overviewLoading = true;
+      _overviewNotFound = false;
+      _overviewError = null;
+    });
+
+    final baseUrl = await _baseUrl();
+    if (!mounted || requestId != _overviewRequestId) return;
+    if (baseUrl == null) {
+      setState(() {
+        _overviewLoading = false;
+        _overviewError = '未配置 API 地址，请前往设置';
+      });
+      return;
+    }
+
+    final result = await _apiService.fetchPaichaOverview(
+      baseUrl: baseUrl,
+      zongpaiNo: zongpaiNo,
+    );
+    if (!mounted || requestId != _overviewRequestId) return;
+
+    setState(() {
+      _overviewLoading = false;
+      if (result.success) {
+        _overview = result;
+        _overviewNotFound = false;
+        _overviewError = null;
+      } else if (result.notFound) {
+        _overview = null;
+        _overviewNotFound = true;
+        _overviewError = null;
+      } else {
+        _overviewError = result.errorMessage ?? '加载失败，点击重试';
+      }
+    });
+  }
+
+  Future<void> _refreshCurrentOverview() async {
+    final zongpaiNo = _overviewZongpaiNo;
+    if (zongpaiNo == null) return;
+    await _loadOverview(zongpaiNo, force: true);
+  }
+}