labels: one module knows how to draw a code, seven views stop guessing

Three core pages and four plugin pages each imported qrcode and jsbarcode
directly, and each carried its own answer to the same questions: what margin,
what width, which error correction, how big a module must be before a scanner
can read it. The answers had already drifted - margin 0 in one place and 2 in
another, width 150 against 160 - and on a label that is the difference between
a sticker that scans and one that does not.

frontend/src/utils/codes.js owns it now: the label-stock presets, the quiet-zone
and margin defaults, CODE128 with no printed value, and the printer-resolution
arithmetic that only the Tech Tools generator had. A view passes what is
specific to its own label and nothing else - MachineBadge still asks for CODE39,
because the badge readers predate the shop-floor scanners and decode nothing
else, and that is exactly the kind of thing a call site should say out loud.

views/print/qrLogo.js is folded in rather than left as a second half-shared
helper that only some of the pages reached into.

The check script now fails a build that imports either library outside that
module. Without it this re-forks within a month: the next label page starts by
copying the nearest existing one, which is how it happened the first time.

Tests cover the part no amount of looking at a screen verifies - a QR that
looks fine at 96 dpi on a monitor can be unreadable at 203 dpi on half-inch
stock.

frontend/src/views/print/AssetLabelBatch.vue

@@ -140,8 +140,7 @@
 <script setup>
 import { ref, computed, onMounted, watch, nextTick } from 'vue'
 import { useRoute } from 'vue-router'
-import JsBarcode from 'jsbarcode'
-import { renderQrDataUrl } from './qrLogo'
+import { renderQrDataUrl, barcodeInto } from '@/utils/codes'
 import { getSetting } from '@/utils/siteSettings'
 import {
   TYPE_CONFIG, hasLocationType, resolveDefaultEncodes,
@@ -273,10 +272,7 @@ function renderBarcodes() {
     const text = codeMap.value[asset.assetid]
     if (!el || !text) continue
     try {
-      JsBarcode(el, text, {
-        format: 'CODE128', displayValue: false, width, height, margin: 0,
-        background: 'transparent',
-      })
+      barcodeInto(el, text, { width, height, background: 'transparent' })
     } catch (err) {
       console.error('Barcode error:', asset.assetnumber, err)
     }