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.

scripts/check-naming-and-style.sh

@@ -140,6 +140,24 @@ fi
 # cannot see and did not choose. Use a setting with a NEUTRAL default, a
 # site-namespaced directory (scripts/site_imports/<site>/), or seed data.
 #
+# Code generation lives in one module. Seven views were importing qrcode and
+# jsbarcode directly, each with its own margin, width and error correction, and
+# the answers had already drifted - which on a label means one page scans and
+# another does not. frontend/src/utils/codes.js owns that knowledge now; a view
+# passes what is specific to its label and nothing else.
+echo "==> Checking that only the shared module imports the code libraries..."
+CODE_LIB_IMPORTS=$(grep -rn "from ['\"]\(qrcode\|jsbarcode\)['\"]" \
+    --include='*.vue' --include='*.js' \
+    frontend/src plugins/ 2>/dev/null \
+    | grep -v 'frontend/src/utils/codes\.js' \
+    | grep -v '\.plugins-staged/' || true)
+if [ -n "$CODE_LIB_IMPORTS" ]; then
+    echo "FAIL: import qrcode/jsbarcode through @/utils/codes, not directly:"
+    echo "$CODE_LIB_IMPORTS"
+    echo
+    VIOLATIONS=$((VIOLATIONS + 1))
+fi
+
 # ENFORCING. It was report-only while the backlog was worked off, and the hit
 # count then did not move for weeks - a rule that only prints is read as no rule.
 # Set SITE_LITERALS_ENFORCE=0 to drop back to reporting for a local run.