refactor: fix unused imports after server recommendation removal

- Remove unused sendMessage import from openai-service.ts
- Mark chatIdStr as unused with underscore prefix

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/openai-service.ts

@@ -10,7 +10,6 @@ import { processTroubleshootConsultation, hasTroubleshootSession } from './agent
 import { processDomainConsultation, hasDomainSession } from './agents/domain-agent';
 import { processDepositConsultation, hasDepositSession } from './agents/deposit-agent';
 import { processDdosConsultation, hasDdosSession } from './agents/ddos-agent';
-import { sendMessage } from './telegram';
 
 const logger = createLogger('openai');
 
@@ -205,7 +204,7 @@ export async function generateOpenAIResponse(
   recentContext: { role: 'user' | 'assistant'; content: string }[],
   telegramUserId?: string,
   db?: D1Database,
-  chatIdStr?: string
+  _chatIdStr?: string  // Unused after server recommendation removal, kept for API compatibility
 ): Promise<string> {
   // Check if troubleshoot session is active
   if (telegramUserId && env.DB) {