Add the printedparts plugin: 3D-printed parts storefront and kiosk

Catalog with photos and append-only print-file revisions, a stock
ledger attributing every take/restock/adjust to a badge-resolved
employee, a touch kiosk (scan bin, scan badge, keypad quantity) with a
deliberately open decrement-only take endpoint, 1x0.5in CODE128 bin
labels, low-stock email alerts to selected users, roles, or addresses,
and stock/consumption/by-person reports with a cache-vs-ledger
reconcile. Ships disabled; enable per site. Contract 0.13.0 adds the
mailer and the User/Role models to the plugin surface.

plugins/printedparts/manifest.json

@@ -0,0 +1,11 @@
+{
+    "name": "printedparts",
+    "version": "0.1.0",
+    "description": "3D-printed parts inventory + kiosk checkout",
+    "display_name": "3D Printed Parts",
+    "author": "",
+    "dependencies": ["employees"],
+    "core_version": ">=0.12.0,<1.0.0",
+    "api_prefix": "/api/printedparts",
+    "default_enabled": false
+}