Create the venv with --system-site-packages so it can import the Pi system packages
that are not pip wheels (hailo_platform via hailo-all, picamera2 via python3-picamera2).
Add CAMERA_BACKEND/CSI_DEVICE to the env template and document the Hailo-8 + CSI
prerequisites and air-gap handling in deploy/README.
Offline-installable bundle (wheelhouse + model + source) built on a machine with
internet and installed on the air-gapped Pi with --no-index (zero fetches), plus a
systemd unit (auto-restart, device access, hardening) and env template. Runs the
package from source via python -m edge (no offline build backend). Drift-guard test
keeps the env template in sync with what the daemon reads and rejects inline comments
that systemd EnvironmentFile= would fold into values.
