fix: properly escape credentials variable in bash script (#24)

The escaped_credentials variable was using single quotes which prevented
proper shell expansion. Changed to double quotes to allow variable
substitution while maintaining safety.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-authored-by: Claude <[email protected]>

Author: z-br

server/utils/code_task_v2.py

@@ -271,7 +271,7 @@ def _run_ai_code_task_v2_internal(task_id: int, user_id: str, github_token: str)
     mkdir -p ~/.claude
     
     # Write credentials content directly to file
-    if [ ! -z '{escaped_credentials}' ]; then
+    if [ ! -z "{escaped_credentials}" ]; then
         echo "📋 Writing credentials to ~/.claude/.credentials.json"
         cat << 'CREDENTIALS_EOF' > ~/.claude/.credentials.json
 {credentials_content}