b49b2b36e0
Code review fixes (commit 92da6aa):
- LST refresh buffer / fallback TTL extracted as named module constants
- Replace `assert` with explicit `if/raise` (asserts stripped under -O)
- Move IBKRAuthError above OAuth1aSigner (forward declaration)
- async_client import lifted to module level
- Test uses actual prime (23) instead of composite (255)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>