Add type checking for output2 response from get_overseas_balance API.
The API can return either list format [{}] or dict format {}, causing
KeyError when accessing output2[0].
Changes:
- Check isinstance before accessing output2[0]
- Handle list, dict, and empty cases
- Add safe fallback with "or" for empty strings
- Add 3 test cases for list/dict/empty formats
Fixes: #41
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>