chore: 全面规范化代码，遵循 CLAUDE.md 编码规范

- C# 文件命名改为 snake_case（28 个文件重命名）
- C# 类转换为主构造函数（8 个类）
- 空 catch 添加异常类型（2 处）
- 新建 GlobalUsings.cs（Health.Infrastructure、Health.WebApi）
- Flutter 移除 go_router，改用 Riverpod 路由栈
- Flutter 移除 flutter_secure_storage，改用 sqflite 持久化
- 修复 Flutter 构建路径（Flutter SDK 迁至 D 盘）
- 后端端口改为 0.0.0.0:5000，支持局域网访问

backend/src/Health.Infrastructure/Data/data_seeder.cs

@@ -0,0 +1,45 @@
+namespace Health.Infrastructure.Data;
+
+/// <summary>
+/// 数据库种子数据
+/// </summary>
+public static class DataSeeder
+{
+    public static async Task SeedAsync(AppDbContext db)
+    {
+        // 种子医生数据
+        if (!db.Doctors.Any())
+        {
+            db.Doctors.AddRange(
+                new Doctor
+                {
+                    Id = Guid.NewGuid(),
+                    Name = "王建国",
+                    Title = "主任医师",
+                    Department = "心血管内科",
+                    Introduction = "擅长冠心病术后管理、心脏康复指导",
+                    IsActive = true
+                },
+                new Doctor
+                {
+                    Id = Guid.NewGuid(),
+                    Name = "李芳",
+                    Title = "副主任医师",
+                    Department = "营养科",
+                    Introduction = "擅长术后营养指导、膳食规划",
+                    IsActive = true
+                },
+                new Doctor
+                {
+                    Id = Guid.NewGuid(),
+                    Name = "张明",
+                    Title = "主任医师",
+                    Department = "心脏康复科",
+                    Introduction = "擅长心脏术后运动康复、心肺功能评估",
+                    IsActive = true
+                }
+            );
+            await db.SaveChangesAsync();
+        }
+    }
+}