Interactive loop around lamp_export.py: scan an EAN (checksum
validated, optional for barcode-less lamps), resolve it against
previous lamps / a local cache / upcitemdb.com, confirm
identification, record the packaging's advertised values, measure
per the published procedure, and commit the bundle to the
comparison-data repo with a device page stub for the web repo.
Every lamp is keyed by an internal ID (L0001, L0002, ...) so one EAN
can cover several versions (daylight/warm white variants) and
unbranded lamps work. lamp_export.py passes optional ean, variant,
and rated (advertised values) fields through into metrics.json.
