feat: 重构数据库迁移架构，支持多数据库提供程序 (SQLite/SQLServer/PostgreSQL/MySQL)

- 将迁移文件按数据库类型分目录存放 (Migrations/SQLite, MySQL, PostgreSQL, SqlServer)
- 新增各数据库提供程序的 DesignTimeDbContextFactory，支持 --provider 参数切换
- 新增 ProviderAppDataContexts，定义各数据库对应的 AppDataContext 子类
- DatabaseExtensions 增加 AddProviderAppDataContext 方法，按配置自动注册对应 DbContext
- 修正 MySQL 提供程序调用方式 (UseMySql -> UseMySQL)
- UserEntity 模型增加新字段
- 更新 add-migration.ps1

Avalonia-EFCore/Database/AppDataContextFactory.cs

@@ -13,9 +13,92 @@ namespace Avalonia_EFCore.Database
         /// <param name="args">命令行参数。</param>
         /// <returns>配置好的数据上下文实例。</returns>
         public AppDataContext CreateDbContext(string[] args)
+        {
+            return new AppDataContext(DesignTimeDatabaseConfiguration.Create(args));
+        }
+    }
+
+    /// <summary>
+    /// SQLite 迁移设计时工厂。
+    /// </summary>
+    public sealed class SqliteAppDataContextFactory : IDesignTimeDbContextFactory<SqliteAppDataContext>
+    {
+        /// <inheritdoc />
+        public SqliteAppDataContext CreateDbContext(string[] args)
+            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.SQLite));
+    }
+
+    /// <summary>
+    /// SQL Server 迁移设计时工厂。
+    /// </summary>
+    public sealed class SqlServerAppDataContextFactory : IDesignTimeDbContextFactory<SqlServerAppDataContext>
+    {
+        /// <inheritdoc />
+        public SqlServerAppDataContext CreateDbContext(string[] args)
+            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.SqlServer));
+    }
+
+    /// <summary>
+    /// PostgreSQL 迁移设计时工厂。
+    /// </summary>
+    public sealed class PostgreSqlAppDataContextFactory : IDesignTimeDbContextFactory<PostgreSqlAppDataContext>
+    {
+        /// <inheritdoc />
+        public PostgreSqlAppDataContext CreateDbContext(string[] args)
+            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.PostgreSQL));
+    }
+
+    /// <summary>
+    /// MySQL 迁移设计时工厂。
+    /// </summary>
+    public sealed class MySqlAppDataContextFactory : IDesignTimeDbContextFactory<MySqlAppDataContext>
+    {
+        /// <inheritdoc />
+        public MySqlAppDataContext CreateDbContext(string[] args)
+            => new(DesignTimeDatabaseConfiguration.Create(args, DatabaseProvider.MySQL));
+    }
+
+    internal static class DesignTimeDatabaseConfiguration
+    {
+        public static DatabaseConfiguration Create(string[] args, DatabaseProvider defaultProvider = DatabaseProvider.SQLite)
         {
             DatabaseProviderRegistry.RegisterDefaults();
-            return new AppDataContext(DatabaseConfiguration.ForSQLite("avalonia-api.db"));
+
+            var provider = GetProvider(args) ?? defaultProvider;
+            return provider switch
+            {
+                DatabaseProvider.SQLite => DatabaseConfiguration.ForSQLite("avalonia-api.db"),
+                DatabaseProvider.SqlServer => DatabaseConfiguration.ForSqlServer("(localdb)\\MSSQLLocalDB", "AvaloniaApi"),
+                DatabaseProvider.PostgreSQL => DatabaseConfiguration.ForPostgreSQL("localhost", "avalonia_api", "postgres", "postgres"),
+                DatabaseProvider.MySQL => DatabaseConfiguration.ForMySQL("localhost", "avalonia_api", "root", "root"),
+                _ => DatabaseConfiguration.ForSQLite("avalonia-api.db"),
+            };
+        }
+
+        private static DatabaseProvider? GetProvider(string[] args)
+        {
+            for (var i = 0; i < args.Length; i++)
+            {
+                var arg = args[i];
+                string? value = null;
+
+                if (arg.Equals("--provider", StringComparison.OrdinalIgnoreCase) && i + 1 < args.Length)
+                {
+                    value = args[i + 1];
+                }
+                else if (arg.StartsWith("--provider=", StringComparison.OrdinalIgnoreCase))
+                {
+                    value = arg["--provider=".Length..];
+                }
+
+                if (!string.IsNullOrWhiteSpace(value)
+                    && Enum.TryParse<DatabaseProvider>(value, ignoreCase: true, out var provider))
+                {
+                    return provider;
+                }
+            }
+
+            return null;
         }
     }
 }

Avalonia-EFCore/Database/DatabaseExtensions.cs

@@ -1,3 +1,4 @@
+using Microsoft.EntityFrameworkCore;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Avalonia_EFCore.Database
@@ -19,6 +20,14 @@ namespace Avalonia_EFCore.Database
             // 注册配置
             services.AddSingleton(config);
 
+            if (typeof(TContext) == typeof(AppDataContext))
+            {
+                services.AddProviderAppDataContext(config);
+                services.AddScoped<DatabaseManager<TContext>>();
+
+                return services;
+            }
+
             // 注册 DbContext
             services.AddDbContext<TContext>(options =>
             {
@@ -31,6 +40,31 @@ namespace Avalonia_EFCore.Database
             return services;
         }
 
+        private static void AddProviderAppDataContext(this IServiceCollection services, DatabaseConfiguration config)
+        {
+            switch (config.Provider)
+            {
+                case DatabaseProvider.SQLite:
+                    services.AddDbContext<AppDataContext, SqliteAppDataContext>(options =>
+                        AppDbContext.ConfigureProvider(options, config));
+                    break;
+                case DatabaseProvider.SqlServer:
+                    services.AddDbContext<AppDataContext, SqlServerAppDataContext>(options =>
+                        AppDbContext.ConfigureProvider(options, config));
+                    break;
+                case DatabaseProvider.PostgreSQL:
+                    services.AddDbContext<AppDataContext, PostgreSqlAppDataContext>(options =>
+                        AppDbContext.ConfigureProvider(options, config));
+                    break;
+                case DatabaseProvider.MySQL:
+                    services.AddDbContext<AppDataContext, MySqlAppDataContext>(options =>
+                        AppDbContext.ConfigureProvider(options, config));
+                    break;
+                default:
+                    throw new NotSupportedException($"数据库提供程序 {config.Provider} 未注册。");
+            }
+        }
+
         /// <summary>
         /// 初始化数据库（在应用启动时调用一次）。
         /// </summary>

Avalonia-EFCore/Database/DatabaseProviderRegistry.cs

@@ -52,7 +52,7 @@ namespace Avalonia_EFCore.Database
                 opts.UseNpgsql(cs, o => { o.CommandTimeout(timeout); o.EnableRetryOnFailure(3); }));
 
             Register(DatabaseProvider.MySQL, (opts, cs, timeout) =>
-                opts.UseMySql(cs, ServerVersion.AutoDetect(cs), o => { o.CommandTimeout(timeout); o.EnableRetryOnFailure(3); }));
+                opts.UseMySQL(cs, o => o.CommandTimeout(timeout)));
         }
     }
 }

Avalonia-EFCore/Database/ProviderAppDataContexts.cs

@@ -0,0 +1,30 @@
+namespace Avalonia_EFCore.Database
+{
+    /// <summary>
+    /// SQLite 专用 DbContext，用于隔离 SQLite 迁移集。
+    /// </summary>
+    public sealed class SqliteAppDataContext(DatabaseConfiguration dbConfig) : AppDataContext(dbConfig)
+    {
+    }
+
+    /// <summary>
+    /// SQL Server 专用 DbContext，用于隔离 SQL Server 迁移集。
+    /// </summary>
+    public sealed class SqlServerAppDataContext(DatabaseConfiguration dbConfig) : AppDataContext(dbConfig)
+    {
+    }
+
+    /// <summary>
+    /// PostgreSQL 专用 DbContext，用于隔离 PostgreSQL 迁移集。
+    /// </summary>
+    public sealed class PostgreSqlAppDataContext(DatabaseConfiguration dbConfig) : AppDataContext(dbConfig)
+    {
+    }
+
+    /// <summary>
+    /// MySQL 专用 DbContext，用于隔离 MySQL 迁移集。
+    /// </summary>
+    public sealed class MySqlAppDataContext(DatabaseConfiguration dbConfig) : AppDataContext(dbConfig)
+    {
+    }
+}