fix: remove duplicate 'client' declaration in executeSell

The const client = getClient() was declared twice in the same function scope
(line 318 for cancel-orders block, line 371 for the sell loop), causing a
SyntaxError at startup. Removed the redundant second declaration.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/services/executor.js

@@ -368,7 +368,6 @@ export async function executeSell(trade) {
     // Round down to 4 decimal places to avoid sub-unit precision errors
     sharesToSell = Math.floor(sharesToSell * 10000) / 10000;
 
-    const client = getClient();
     let filled = false;
 
     for (let attempt = 1; attempt <= config.maxRetries; attempt++) {