Pins to python3.13 to match the Debian Trixie production target.
Documents the dev setup in README and AGENTS.md so a fresh checkout
gets a working `python` via `direnv allow` + editable installs.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Exclude local agent state from deploy archives, avoid recursive ownership over active runtime mounts, and let Alembic own schema upgrades before app startup.
