Refactor welcome message handling to UserService for Telegram channel updates

- Moved the welcome message logic from UserController to UserService to centralize user notification handling.
- Improved error logging for message sending failures, ensuring better traceability of issues.
- Enhanced user experience by maintaining the detailed setup information and friendly greeting in the welcome message.

src/Managing.Api/Controllers/UserController.cs

@@ -106,37 +106,6 @@ public class UserController : BaseController
     {
         var user = await GetUser();
         var updatedUser = await _userService.UpdateTelegramChannel(user, telegramChannel);
-
-        // Send welcome message to the newly configured telegram channel
-        if (!string.IsNullOrEmpty(telegramChannel))
-        {
-            try
-            {
-                var welcomeMessage = $"🎉 **Welcome to Kaigen Notifications!**\n\n" +
-                                     $"Hello {user.AgentName}! 👋\n\n" +
-                                     $"Your Telegram channel has been successfully configured and you're now connected to the Kaigen notification system.\n\n" +
-                                     $"📋 **Your Setup Details:**\n" +
-                                     $"• 🎯 **Agent Name:** {user.AgentName}\n" +
-                                     $"• 📡 **Channel ID:** {telegramChannel}\n" +
-                                     $"• ⏰ **Connected:** {DateTime.UtcNow:MMM dd, yyyy • HH:mm:ss} UTC\n\n" +
-                                     $"🔔 **What You'll Receive:**\n" +
-                                     $"• 📈 Real-time position opens and closes\n" +
-                                     $"• 💰 Trading activity updates\n" +
-                                     $"• 🤖 Strategy and configuration changes\n" +
-                                     $"• ⚠️ Important system alerts\n\n" +
-                                     $"✨ **You're all set!** Start receiving your trading notifications right away. If you have any questions, feel free to reach out.\n\n" +
-                                     $"Happy trading! 🚀";
-
-                await _webhookService.SendMessage(welcomeMessage, telegramChannel);
-            }
-            catch (Exception ex)
-            {
-                // Log the error but don't fail the update operation
-                Console.WriteLine(
-                    $"Failed to send welcome message to telegram channel {telegramChannel}: {ex.Message}");
-            }
-        }
-
         return Ok(updatedUser);
     }