feat: 后台管理页全量重构 + backoffice 共享模块 + 启动脚本优化

## 后台管理页重构
- admin 端: add_doctor / doctors / home / patients 四页重构
- doctor 端: consultations / dashboard / followup_edit / followups / home / patient_detail / patients / profile / report_detail / reports / settings 十一页重构
- 新增 backoffice 共享模块: backoffice_refresh_providers + backoffice_formatters + backoffice_ui

## 后端
- AdminService 增强(分页/搜索/统计)
- doctor_endpoints 微调
- appsettings.Development 调整
- 新增 admin_service_tests

## 前端其他
- 今日健康卡片 taskRow 行高 5->7(每行 44->48px)
- 健康仪表盘配色定 #4FACFE 纯色蓝
- admin_drawer / doctor_drawer 微调
- api_client IP 适配

## 启动脚本
- start-dev.bat: 加后端就绪检测(轮询 openapi 端点, 最多等 30s)

## 清理
- 删除旧品牌图(agent_welcome_abstract / login_background_v1)
- 删除 app_status_badge 组件
- 删除旧 HANDOFF 文档, 新增 07-17 版

## 测试
- 新增 backoffice_formatters / backoffice_refresh / backoffice_ui 三个测试
- app_router_test 扩展

health_app/test/backoffice_ui_test.dart

@@ -0,0 +1,60 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:health_app/widgets/backoffice_ui.dart';
+
+void main() {
+  testWidgets('backoffice surface provides the shared patient-style canvas', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      const MaterialApp(home: BackofficeSurface(child: Text('内容'))),
+    );
+
+    expect(find.text('内容'), findsOneWidget);
+    expect(find.byType(DecoratedBox), findsWidgets);
+  });
+
+  testWidgets('empty state shows its message and optional action', (
+    tester,
+  ) async {
+    var tapped = false;
+    await tester.pumpWidget(
+      MaterialApp(
+        home: BackofficeEmptyState(
+          icon: Icons.people_outline,
+          title: '暂无患者',
+          description: '患者加入后会显示在这里',
+          actionLabel: '刷新',
+          onAction: () => tapped = true,
+        ),
+      ),
+    );
+
+    expect(find.text('暂无患者'), findsOneWidget);
+    expect(find.text('患者加入后会显示在这里'), findsOneWidget);
+    await tester.tap(find.text('刷新'));
+    expect(tapped, isTrue);
+  });
+
+  testWidgets('error state exposes a retry action', (tester) async {
+    var retried = false;
+    await tester.pumpWidget(
+      MaterialApp(home: BackofficeErrorState(onRetry: () => retried = true)),
+    );
+
+    expect(find.text('加载失败'), findsOneWidget);
+    await tester.tap(find.text('重新加载'));
+    expect(retried, isTrue);
+  });
+
+  testWidgets('inactive doctor banner explains the registration impact', (
+    tester,
+  ) async {
+    await tester.pumpWidget(
+      const MaterialApp(home: BackofficeInactiveDoctorBanner()),
+    );
+
+    expect(find.text('账号已停用'), findsOneWidget);
+    expect(find.textContaining('新患者暂时无法选择您'), findsOneWidget);
+  });
+}