fix:修复已知问题

backend/IM_API/Migrations/20260208124430_update-group.cs

@@ -0,0 +1,65 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace IM_API.Migrations
+{
+    /// <inheritdoc />
+    public partial class updategroup : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "LastMessage",
+                table: "groups",
+                type: "longtext",
+                nullable: false,
+                collation: "utf8mb4_general_ci")
+                .Annotation("MySql:CharSet", "utf8mb4");
+
+            migrationBuilder.AddColumn<string>(
+                name: "LastSenderName",
+                table: "groups",
+                type: "longtext",
+                nullable: false,
+                collation: "utf8mb4_general_ci")
+                .Annotation("MySql:CharSet", "utf8mb4");
+
+            migrationBuilder.AddColumn<DateTimeOffset>(
+                name: "LastUpdateTime",
+                table: "groups",
+                type: "datetime(6)",
+                nullable: false,
+                defaultValue: new DateTimeOffset(new DateTime(1, 1, 1, 0, 0, 0, 0, DateTimeKind.Unspecified), new TimeSpan(0, 0, 0, 0, 0)));
+
+            migrationBuilder.AddColumn<long>(
+                name: "MaxSequenceId",
+                table: "groups",
+                type: "bigint",
+                nullable: false,
+                defaultValue: 0L);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "LastMessage",
+                table: "groups");
+
+            migrationBuilder.DropColumn(
+                name: "LastSenderName",
+                table: "groups");
+
+            migrationBuilder.DropColumn(
+                name: "LastUpdateTime",
+                table: "groups");
+
+            migrationBuilder.DropColumn(
+                name: "MaxSequenceId",
+                table: "groups");
+        }
+    }
+}

backend/IM_API/Migrations/ImContextModelSnapshot.cs

@@ -354,6 +354,20 @@ namespace IM_API.Migrations
                         .HasColumnType("int(11)")
                         .HasComment("群主");
 
+                    b.Property<string>("LastMessage")
+                        .IsRequired()
+                        .HasColumnType("longtext");
+
+                    b.Property<string>("LastSenderName")
+                        .IsRequired()
+                        .HasColumnType("longtext");
+
+                    b.Property<DateTimeOffset>("LastUpdateTime")
+                        .HasColumnType("datetime(6)");
+
+                    b.Property<long>("MaxSequenceId")
+                        .HasColumnType("bigint");
+
                     b.Property<string>("Name")
                         .IsRequired()
                         .HasMaxLength(20)