feat: add low-stock threshold field to EditItemModal (#67)

app/components/inventory/EditItemModal.vue

@@ -55,6 +55,21 @@
           />
         </UFormGroup>
 
+        <!-- Low Stock Threshold -->
+        <UFormGroup 
+          label="Low Stock Alert" 
+          hint="Optional - Alert when quantity falls below this"
+        >
+          <UInput 
+            v-model.number="form.low_stock_threshold"
+            type="number"
+            min="0"
+            step="0.1"
+            placeholder="e.g. 2"
+            size="lg"
+          />
+        </UFormGroup>
+
         <!-- Notes -->
         <UFormGroup label="Notes" hint="Optional">
           <UTextarea
@@ -112,6 +127,7 @@ const form = reactive({
   quantity: 1,
   unit_id: '',
   expiry_date: '',
+  low_stock_threshold: null as number | null,
   notes: ''
 })
 
@@ -136,6 +152,7 @@ watch(() => props.item, (newItem) => {
     form.quantity = Number(newItem.quantity)
     form.unit_id = newItem.unit_id
     form.expiry_date = newItem.expiry_date || ''
+    form.low_stock_threshold = newItem.low_stock_threshold || null
     form.notes = newItem.notes || ''
     isOpen.value = true
   }
@@ -168,6 +185,7 @@ const handleSubmit = async () => {
     quantity: form.quantity,
     unit_id: form.unit_id,
     expiry_date: form.expiry_date || null,
+    low_stock_threshold: form.low_stock_threshold,
     notes: form.notes.trim() || null
   })