Fix JWT token refresh bug and code quality improvements

[ms32035]

Summary

• Fix inverted JWT token expiry check in _refresh_jwt_token() — tokens were being re-fetched on every request instead of being cached
• Strip trailing slash from host in __init__ to prevent double-slash URLs
• Fix import_transactions() silently discarding the API response — now returns dict[str, Any]
• Modernise all docstring type annotations from Dict/Optional to dict/X | None
• Add CLAUDE.md with project guidance for Claude Code
• Add GitHub Actions release workflow for PyPI publishing via OIDC trusted publisher
• Bump ruff pre-commit hook to v0.15.7
• Bump version to 0.8.1, requires-python to >=3.11