fix issues

ChatBot/Services/HistoryCompressionService.cs

@@ -246,7 +246,10 @@ namespace ChatBot.Services
                 if (content.Length < _aiSettings.MinMessageLengthForSummarization)
                 {
                     return content.Length > _aiSettings.MaxSummarizedMessageLength
-                        ? content.Substring(0, _aiSettings.MaxSummarizedMessageLength) + "..."
+                        ? string.Concat(
+                            content.AsSpan(0, _aiSettings.MaxSummarizedMessageLength),
+                            "..."
+                        )
                         : content;
                 }
 
@@ -267,10 +270,13 @@ namespace ChatBot.Services
                 var summary = await GenerateSummaryAsync(summaryMessages, cancellationToken);
 
                 return string.IsNullOrEmpty(summary)
-                    ? content.Substring(
-                        0,
-                        Math.Min(content.Length, _aiSettings.MaxSummarizedMessageLength)
-                    ) + "..."
+                    ? string.Concat(
+                        content.AsSpan(
+                            0,
+                            Math.Min(content.Length, _aiSettings.MaxSummarizedMessageLength)
+                        ),
+                        "..."
+                    )
                     : summary;
             }
             catch (Exception ex)
@@ -345,7 +351,7 @@ namespace ChatBot.Services
 
             var result = response.ToString().Trim();
             return result.Length > _aiSettings.MaxSummarizedMessageLength
-                ? result.Substring(0, _aiSettings.MaxSummarizedMessageLength) + "..."
+                ? string.Concat(result.AsSpan(0, _aiSettings.MaxSummarizedMessageLength), "...")
                 : result;
         }
 
@@ -419,8 +425,10 @@ namespace ChatBot.Services
             return new ChatMessage
             {
                 Role = message.Role,
-                Content =
-                    message.Content.Substring(0, _aiSettings.MaxSummarizedMessageLength) + "...",
+                Content = string.Concat(
+                    message.Content.AsSpan(0, _aiSettings.MaxSummarizedMessageLength),
+                    "..."
+                ),
             };
         }
     }

ChatBot/Services/Telegram/Commands/CommandRegistry.cs

@@ -8,7 +8,9 @@ namespace ChatBot.Services.Telegram.Commands
     /// </summary>
     public class CommandRegistry
     {
-        private readonly Dictionary<string, ITelegramCommand> _commands = new();
+        private readonly Dictionary<string, ITelegramCommand> _commands = new(
+            StringComparer.OrdinalIgnoreCase
+        );
         private readonly ILogger<CommandRegistry> _logger;
 
         public CommandRegistry(
@@ -32,12 +34,9 @@ namespace ChatBot.Services.Telegram.Commands
         /// </summary>
         private void RegisterCommand(ITelegramCommand command)
         {
-            if (command == null)
-            {
-                throw new ArgumentNullException(nameof(command));
-            }
+            ArgumentNullException.ThrowIfNull(command);
 
-            var commandName = command.CommandName.ToLower();
+            var commandName = command.CommandName;
             if (_commands.ContainsKey(commandName))
             {
                 _logger.LogWarning("Command '{CommandName}' is already registered", commandName);
@@ -53,8 +52,7 @@ namespace ChatBot.Services.Telegram.Commands
         /// </summary>
         public ITelegramCommand? GetCommand(string commandName)
         {
-            var key = commandName.ToLower();
-            return _commands.TryGetValue(key, out var command) ? command : null;
+            return _commands.TryGetValue(commandName, out var command) ? command : null;
         }
 
         /// <summary>

ChatBot/Services/Telegram/Commands/TelegramCommandBase.cs

@@ -47,7 +47,7 @@ namespace ChatBot.Services.Telegram.Commands
                 command = command.Split('@')[0];
             }
 
-            return command == CommandName.ToLower();
+            return string.Equals(command, CommandName, StringComparison.OrdinalIgnoreCase);
         }
 
         /// <summary>

ChatBot/Services/Telegram/Services/TelegramMessageHandler.cs

@@ -65,7 +65,7 @@ namespace ChatBot.Services.Telegram.Services
                     messageText,
                     chatId,
                     userName,
-                    message.Chat.Type.ToString().ToLower(),
+                    message.Chat.Type.ToString(),
                     message.Chat.Title ?? "",
                     replyInfo,
                     cancellationToken