printedparts stage 2: models, real 0001 baseline, tables live

PrintedItem (catalog: code, name, image, cached quantityonhand,
per-item threshold, bin) and PrintedItemTransaction (the ledger:
signed quantity change attributed to a badge-resolved employee).
Both registered in PLUGIN_TABLE_OWNERS; 0001 is a post-cutover real
baseline. The migration-guard test learns the new expected head.
Routes are a placeholder ping until the next stage - the scaffold's
list route imported the deleted scaffold model, which surfaces as an
empty 'Migration error' because the alembic env imports the models
package.

shopdb/plugins/alembic_template.py

@@ -53,6 +53,7 @@ PLUGIN_TABLE_OWNERS: dict[str, Iterable[str]] = {
     'measuringtools': ('measuringtooltypes', 'measuringtools'),
     'network':       ('networkdevicetypes', 'networkdevices', 'vlans', 'subnets'),
     'notifications': ('notificationtypes', 'notifications'),
+    'printedparts':  ('printeditems', 'printeditemtransactions'),
     'printers':      ('printertypes', 'printers', 'modelsupplies', 'printerdrivers'),
     'slides':        ('tvslides',),
     'usb':           ('usbdevicetypes', 'usbdevices', 'usbcheckouts'),