fix(orders): Prevent premature shipping rate fetching

## Issues Fixed:

### 1. Shipping rates fetched on page load ✅
**Problem:**
- Open New Order form → Shipping already calculated
- Using cached/legacy values
- Should wait for address to be filled

**Solution:**
Added address completeness check:
```ts
const isShippingAddressComplete = useMemo(() => {
  if (!shippingData.country) return false;
  if (!shippingData.city) return false;

  // If country has states, require state
  const countryStates = states[shippingData.country];
  if (countryStates && Object.keys(countryStates).length > 0) {
    if (!shippingData.state) return false;
  }

  return true;
}, [shippingData.country, shippingData.state, shippingData.city]);
```

Query only enabled when address is complete:
```ts
enabled: isShippingAddressComplete && items.length > 0
```

### 2. Unnecessary refetches ✅
**Problem:**
- Every keystroke triggered refetch
- staleTime: 0 meant always refetch

**Solution:**
```ts
staleTime: 5 * 60 * 1000 // Cache for 5 minutes
```

Query key still includes all address fields, so:
- Change country → Refetch (key changed)
- Change state → Refetch (key changed)
- Change city → Refetch (key changed)
- Change postcode → Refetch (key changed)
- Same values → Use cache (key unchanged)

### 3. Order preview fetching too early ✅
**Problem:**
- Preview calculated before shipping method selected
- Incomplete data

**Solution:**
```ts
enabled: items.length > 0 && !!bCountry && !!shippingMethod
```

## New Behavior:

### On Page Load:
- ❌ No shipping fetch
- ❌ No preview fetch
- ✅ Clean state

### User Fills Address:
1. Enter country → Not enough
2. Enter state → Not enough
3. Enter city → ✅ **Fetch shipping rates**
4. Rates appear → First auto-selected
5. ✅ **Fetch order preview** (has method now)

### User Changes Address:
1. Change Jakarta → Bandung
2. Query key changes (city changed)
3. ✅ **Refetch shipping rates**
4. New rates appear → First auto-selected
5. ✅ **Refetch order preview**

### User Types in Same Field:
1. Type "Jak..." → "Jakarta"
2. Query key same (city still "Jakarta")
3. ❌ No refetch (use cache)
4. Efficient!

## Benefits:
- ✅ No premature fetching
- ✅ No unnecessary API calls
- ✅ Smart caching (5 min)
- ✅ Only refetch when address actually changes
- ✅ Better UX and performance

admin-spa/src/routes/Orders/partials/OrderForm.tsx

@@ -185,25 +185,36 @@ export default function OrderForm({
     enabled: items.length > 0,
   });
 
+  // Check if shipping address is complete enough to calculate rates
+  const isShippingAddressComplete = React.useMemo(() => {
+    // Need at minimum: country, state (if applicable), city
+    if (!shippingData.country) return false;
+    if (!shippingData.city) return false;
+    // If country has states, require state
+    const countryStates = states[shippingData.country];
+    if (countryStates && Object.keys(countryStates).length > 0 && !shippingData.state) {
+      return false;
+    }
+    return true;
+  }, [shippingData.country, shippingData.state, shippingData.city, states]);
+
   // Calculate shipping rates dynamically
   const { data: shippingRates, isLoading: shippingLoading } = useQuery({
     queryKey: ['shipping-rates', items.map(i => ({ product_id: i.product_id, qty: i.qty })), shippingData.country, shippingData.state, shippingData.city, shippingData.postcode, shippingData.address_1],
     queryFn: async () => {
-      if (!shippingData.country) return null;
       return api.post('/shipping/calculate', {
         items: items.map(i => ({ product_id: i.product_id, qty: i.qty })),
         shipping: shippingData,
       });
     },
-    enabled: !!shippingData.country && items.length > 0,
-    staleTime: 0, // Always refetch when query key changes
+    enabled: isShippingAddressComplete && items.length > 0,
+    staleTime: 5 * 60 * 1000, // Cache for 5 minutes - only refetch if query key changes
   });
 
   // Calculate order preview with taxes
   const { data: orderPreview, isLoading: previewLoading } = useQuery({
     queryKey: ['order-preview', items.map(i => ({ product_id: i.product_id, qty: i.qty })), bCountry, bState, bPost, bCity, shippingData.country, shippingData.state, shippingData.city, shippingData.postcode, shippingMethod, validatedCoupons.map(c => c.code)],
     queryFn: async () => {
-      if (items.length === 0) return null;
       return api.post('/orders/preview', {
         items: items.map(i => ({ product_id: i.product_id, qty: i.qty })),
         billing: { country: bCountry, state: bState, postcode: bPost, city: bCity },
@@ -212,8 +223,8 @@ export default function OrderForm({
         coupons: validatedCoupons.map(c => c.code),
       });
     },
-    enabled: items.length > 0 && !!bCountry,
-    staleTime: 0, // Always refetch when query key changes
+    enabled: items.length > 0 && !!bCountry && !!shippingMethod,
+    staleTime: 5 * 60 * 1000, // Cache for 5 minutes - only refetch if query key changes
   });
 
   // --- Product search for Add Item ---