Add Code 39 barcode format to barcode generator tool

Feature: Support Code 39 symbology alongside existing QR and CODE128
- Added CODE39 option to code type dropdown (front and back sides)
- Updated renderOne() to handle code39 type with format parameter
- Code 39 shares CSS styling with CODE128 (linear barcode layout)
- Updated error message to be format-agnostic

Use case: Legacy systems and equipment that require Code 39 format
for compatibility (common in manufacturing and inventory systems)

Technical notes:
- JsBarcode library already supports CODE39 format
- Passed format parameter to barcodeSvgDataUri() function
- Both CODE128 and CODE39 use .type-barcode CSS class

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

plugins/tools/frontend/views/CodeGenerator.vue

@@ -40,6 +40,7 @@
             <select v-model="codetype">
               <option value="qr">QR</option>
               <option value="barcode">CODE128</option>
+              <option value="code39">CODE39</option>
             </select>
           </label>
           <label v-if="codetype === 'qr'">
@@ -242,6 +243,7 @@
                 <option value="same">Same as the front</option>
                 <option value="qr">QR</option>
                 <option value="barcode">CODE128</option>
+                <option value="code39">CODE39</option>
               </select>
             </label>
             <label>
@@ -301,7 +303,7 @@
           - split the CSV and print it in batches.
         </p>
         <p v-if="overlong.length" class="control-note">
-          {{ overlong.length }} row(s) could not be encoded as CODE128 or were empty:
+          {{ overlong.length }} row(s) could not be encoded or were empty:
           {{ overlong.slice(0, 3).join(', ') }}{{ overlong.length > 3 ? ' ...' : '' }}
         </p>
         </div>
@@ -475,9 +477,12 @@ function showPicture(page) {
 }
 
 function labelClasses(page) {
+  const type = codeTypeFor(page)
+  // code39 and barcode (CODE128) share the same CSS class for linear barcode layout
+  const typeClass = type === 'code39' ? 'barcode' : type
   return [
     'layout-' + layoutFor(page),
-    'type-' + codeTypeFor(page),
+    'type-' + typeClass,
     'side-' + page.side,
     showPicture(page) && pictureposition.value !== 'behind' ? 'pic-' + pictureposition.value : '',
   ]
@@ -588,9 +593,13 @@ const fitAdvice = computed(() => {
 async function renderOne(page) {
   const text = page.content
   if (!text) return ''
-  if (codeTypeFor(page) === 'qr') {
+  const type = codeTypeFor(page)
+  if (type === 'qr') {
     return qrSvgDataUri(text, { errorCorrection: errorcorrection.value })
   }
+  if (type === 'code39') {
+    return barcodeSvgDataUri(text, { format: 'CODE39' })
+  }
   return barcodeSvgDataUri(text)
 }