v0.3.0

• HTTP session management: pooled requests.Session, retry with backoff, configure() for timeouts/pool/log level, cleanup on exit (PR #11)
• Fixes: User.get(all_users=True)/add() trailing-slash 404, non-portable date_diff(), Account.get_accountid() returning int instead of str
• Test suite expanded to 88% coverage with real (non-mocked) integration/local-server tests
• Docs: consistent SonetelUsername/SonetelPassword env var casing, restored CHANGELOG.md 0.2.1 entry, coverage badge
• Tooling: fixed pre-commit formatter oscillation (isort/black/autopep8), bumped autopep8 for Python 3.14 build support