printedparts stage 8: 1x0.5in bin labels

New public print view at /print/printedparts-labels following the
plugin-owned USB label precedent: multi-select with per-item copies,
CODE128 of the item code via JsBarcode (a QR at this size is at the
edge of scanner tolerance), one label per page on 1in x 0.5in roll
stock via a new @page size. The Detail page's Bin Label button
preselects its item through ?item=<id>; the list header gains a batch
Print Labels button.

frontend/src/router/index.js

@@ -117,6 +117,12 @@ const routes = [
     component: () => import('../views/print/USBLabelBatch.vue'),
     meta: { plugin: 'usb' }
   },
+  {
+    path: '/print/printedparts-labels',
+    name: 'print-printedparts-labels',
+    component: () => import('../views/print/PrintedPartsLabels.vue'),
+    meta: { plugin: 'printedparts' }
+  },
   {
     path: '/',
     component: AppLayout,