Update URL immediately when any form field changes

- Add @input handlers to text/number inputs (startNumber, prefix, leadingZeros)
- Add @change handler to checkbox (borderToggle)
- Remove updateUrl() call from generateLabels() since it's now handled by events

The URL now stays in sync with the form state at all times, not just
when clicking "Regenerate Labels".

index.html

@@ -89,6 +89,7 @@
               type="number"
               id="startNumber"
               x-model="startNumber"
+              @input="updateUrl()"
               required
               min="1"
               step="1"
@@ -120,6 +121,7 @@
               type="text"
               id="prefix"
               x-model="prefix"
+              @input="updateUrl()"
               required
               value="ASN"
               class="block w-full rounded-lg border border-gray-300 bg-gray-50 p-2.5 text-sm text-gray-900 focus:border-blue-500 focus:ring-blue-500"
@@ -147,6 +149,7 @@
               type="number"
               id="leadingZeros"
               x-model="leadingZeros"
+              @input="updateUrl()"
               required
               value="5"
               min="0"
@@ -160,6 +163,7 @@
                   type="checkbox"
                   id="borderToggle"
                   x-model="borderToggle"
+                  @change="updateUrl()"
                   class="focus:ring-3 h-4 w-4 rounded border border-gray-300 bg-gray-50 focus:ring-blue-300"
                 />
               </div>
@@ -306,7 +310,6 @@
 
               this.labels.push({ qrCodeUrl, text });
             }
-            this.updateUrl();
           },
           printLabels() {
             window.print();