fix: send actual quantities to pricing engine for correct volume discount calculation in UI

src/components/ModelUploadSection.vue

@@ -427,26 +427,26 @@ onMounted(async () => {
   } catch (e) { console.error("Failed to load initial data:", e); }
 });
 
-watch([() => files.value.length, selectedMaterial, modelLink], async () => {
+watch([() => files.value.map(f => f.quantity), selectedMaterial, modelLink], async () => {
   if ((files.value.length > 0) && selectedMaterial.value) {
     try {
       const res = await getPriceEstimate({
         material_id: parseInt(selectedMaterial.value),
         file_sizes: files.value.map(f => f.size),
-        file_quantities: files.value.map(f => 1), // Only get base unit cost
+        file_quantities: files.value.map(f => f.quantity),
       });
       // Assign individual prices to files for local quantity multiplication
-        if (res.file_prices && Array.isArray(res.file_prices)) {
-          files.value.forEach((f, i) => {
-            f.basePrice = res.file_prices[i];
-          });
-          estimateMetadata.value = res.metadata;
-          // Force reactivity update
-          files.value = [...files.value];
-        }
+      if (res.file_prices && Array.isArray(res.file_prices)) {
+        files.value.forEach((f, i) => {
+          f.basePrice = res.file_prices[i];
+        });
+        estimateMetadata.value = res.metadata;
+        // Force reactivity update
+        files.value = [...files.value];
+      }
     } catch { /* silent */ }
   }
-});
+}, { deep: true });
 
 const isFormValid = computed(() =>
   firstName.value.trim() !== "" && lastName.value.trim() !== "" &&