Revert "fix: mistake in 0c42613"

This reverts commit 8ffd0004b3.

src/backend/src/modules/puterai/ClaudeService.js

@@ -122,7 +122,6 @@ class ClaudeService extends BaseService {
                 
                 const system_prompts = [];
                 for ( let i = messages.length - 1; i >= 0; i-- ) {
-                    const message = messages[i];
                     if ( message.role === 'system' ) {
                         system_prompts.push(...message.content);
                         messages.splice(i, 1);