fix: align backend APIs and upload flow

MessageService.Infrastructure/Configs/ConversationConfig.cs

@@ -11,6 +11,7 @@ namespace MessageService.Infrastructure.Configs
             builder.ToTable("conversations");
             builder.HasKey(x => x.Id);
             builder.HasIndex(x => x.UserId);
+            builder.HasIndex(x => new { x.UserId, x.ChatType, x.TargetId, x.IsDeleted });
 
         }
     }

MessageService.Infrastructure/Migrations/20260909000100_ApiAlignmentFixes.cs

@@ -0,0 +1,25 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace MessageService.Infrastructure.Migrations
+{
+    [DbContext(typeof(MessageDbContext))]
+    [Migration("20260909000100_ApiAlignmentFixes")]
+    public partial class ApiAlignmentFixes : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateIndex(
+                name: "IX_conversations_UserId_ChatType_TargetId_IsDeleted",
+                table: "conversations",
+                columns: new[] { "UserId", "ChatType", "TargetId", "IsDeleted" });
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_conversations_UserId_ChatType_TargetId_IsDeleted",
+                table: "conversations");
+        }
+    }
+}

MessageService.Infrastructure/Migrations/MessageDbContextModelSnapshot.cs

@@ -76,6 +76,8 @@ namespace MessageService.Infrastructure.Migrations
 
                     b.HasIndex("UserId");
 
+                    b.HasIndex("UserId", "ChatType", "TargetId", "IsDeleted");
+
                     b.ToTable("conversations", (string)null);
                 });
 

MessageService.Infrastructure/Reposities/MessageReposity.cs

@@ -26,30 +26,32 @@ namespace MessageService.Infrastructure.Reposities
         public async Task<(IEnumerable<Message> messages, bool hasMore)> GetAsync(string streamKey, long? cusor, int direction, int limit)
         {
             var query = db.Messages.Where(x => x.StreamKey == streamKey);
-            List<Message> messages = [];
+            List<Message> fetched;
             if (direction == 0) // Before: 找比锚点小的，按倒序排
             {
                 if (cusor.HasValue)
                     query = query.Where(m => m.SequenceId < cusor.Value);
 
-                var list = await query
+                fetched = await query
                     .OrderByDescending(m => m.SequenceId) // 最新消息在最前
                     .Take(limit + 1)
                     .ToListAsync();
-
-                messages = [.. list.OrderBy(s => s.SequenceId)];
             }
             else
             {
                 if (cusor is null)
-                    return (messages, false);
+                    return (Array.Empty<Message>(), false);
 
-                messages = await query.OrderBy(o => o.SequenceId)
+                fetched = await query
+                    .Where(m => m.SequenceId > cusor.Value)
+                    .OrderBy(o => o.SequenceId)
                     .Take(limit + 1)
                     .ToListAsync();
             }
 
-            return (messages, messages.Count > limit);
+            var hasMore = fetched.Count > limit;
+            var messages = fetched.Take(limit).OrderBy(s => s.SequenceId).ToList();
+            return (messages, hasMore);
         }
     }
 }