DB: Message + Attachments in einer Transaktion speichern (1x fsync statt N+1)

Services/DatabaseService.cs

@@ -360,18 +360,42 @@ public class DatabaseService
         ", record);
     }
 
-    // ── Attachments ──
-
-    public async Task SaveAttachment(AttachmentRecord attachment)
+    /// <summary>
+    /// Speichert Message + Attachments in einer Transaktion (1x fsync statt N+1).
+    /// </summary>
+    public async Task<long> SaveMessageWithAttachments(MessageRecord record, List<AttachmentRecord> attachments)
     {
         using var conn = CreateConnection();
-        attachment.CreatedAt = DateTime.UtcNow.ToString("o");
-        await conn.ExecuteAsync(@"
-            INSERT INTO attachments (message_id, type, media_type, file_name, data, created_at)
-            VALUES (@MessageId, @Type, @MediaType, @FileName, @Data, @CreatedAt)
-        ", attachment);
+        using var tx = conn.BeginTransaction();
+
+        record.CreatedAt = DateTime.UtcNow.ToString("o");
+        record.AttachmentCount = attachments?.Count ?? 0;
+        var messageId = await conn.ExecuteScalarAsync<long>(@"
+            INSERT INTO messages (chain_id, role, type, content, tool_name, tool_call_id, is_error, iteration, attachment_count, created_at)
+            VALUES (@ChainId, @Role, @Type, @Content, @ToolName, @ToolCallId, @IsError, @Iteration, @AttachmentCount, @CreatedAt);
+            SELECT last_insert_rowid();
+        ", record, tx);
+
+        if (attachments != null)
+        {
+            var now = DateTime.UtcNow.ToString("o");
+            foreach (var att in attachments)
+            {
+                att.MessageId = messageId;
+                att.CreatedAt = now;
+                await conn.ExecuteAsync(@"
+                    INSERT INTO attachments (message_id, type, media_type, file_name, data, created_at)
+                    VALUES (@MessageId, @Type, @MediaType, @FileName, @Data, @CreatedAt)
+                ", att, tx);
+            }
+        }
+
+        tx.Commit();
+        return messageId;
     }
 
+    // ── Attachments ──
+
     public async Task<IEnumerable<AttachmentRecord>> GetAttachments(long messageId)
     {
         using var conn = CreateConnection();