refactor: Remove frontend auto-generation logic, delegate to backend

ARCHITECTURAL CHANGE: Migrated from frontend-based code generation to
backend-based generation following best practices discovered in the orders
service implementation.

RATIONALE:
After investigating the codebase, found that the orders service already
implements proper backend auto-generation for order numbers (ORD-YYYYMMDD-####).
This approach is superior to frontend generation for several reasons:

1. **Uniqueness Guarantee**: Database-enforced uniqueness, no race conditions
2. **Sequential Numbering**: True sequential IDs per tenant per day
3. **Consistent Format**: Server-controlled format ensures consistency
4. **Audit Trail**: Full server-side logging and tracking
5. **Simplicity**: No complex frontend state management
6. **Performance**: One less re-render trigger in wizards

CHANGES MADE:

**InventoryWizard.tsx:**
- ❌ Removed: useRef, useEffect auto-generation logic
- ❌ Removed: SKU generation (SKU-{name}-{timestamp})
- ✅ Changed: SKU field to optional with new placeholder
- ✅ Updated: Tooltip to indicate backend generation
- ✅ Simplified: Removed unnecessary imports (useEffect, useRef)

**QualityTemplateWizard.tsx:**
- ❌ Removed: useRef, useEffect auto-generation logic
- ❌ Removed: Template code generation (TPL-{name}-{timestamp})
- ✅ Changed: Template code field to optional
- ✅ Updated: Placeholder text for clarity
- ✅ Simplified: Removed unnecessary imports

**CustomerOrderWizard.tsx:**
- ❌ Removed: useRef, useEffect auto-generation logic
- ❌ Removed: Order number generation (ORD-{timestamp})
- ✅ Changed: Order number field to read-only/disabled
- ✅ Updated: Shows "Auto-generated on save" placeholder
- ✅ Added: Tooltip explaining backend format (ORD-YYYYMMDD-####)

NEXT STEPS (Backend Implementation Required):
1. Inventory Service: Add SKU generation method (similar to order_number)
2. Production Service: Add template code generation for quality templates
3. Format suggestions:
   - SKU: "SKU-{TENANT_PREFIX}-{SEQUENCE}" or similar
   - Template Code: "TPL-{TYPE_PREFIX}-{SEQUENCE}"

BENEFITS:
- ✅ Eliminates all focus loss issues from auto-generation
- ✅ Removes complex state management from frontend
- ✅ Ensures true uniqueness at database level
- ✅ Better user experience with clear messaging
- ✅ Follows established patterns from orders service
- ✅ Cleaner, more maintainable code

This change completes the frontend simplification. Backend services now
need to implement generation logic similar to orders service pattern.

frontend/src/components/domain/unified-wizard/wizards/CustomerOrderWizard.tsx

@@ -1,4 +1,4 @@
-import React, { useState, useEffect, useRef } from 'react';
+import React, { useState, useEffect } from 'react';
 import { WizardStep, WizardStepProps } from '../../../ui/WizardModal/WizardModal';
 import { AdvancedOptionsSection } from '../../../ui/AdvancedOptionsSection';
 import Tooltip from '../../../ui/Tooltip/Tooltip';
@@ -526,8 +526,6 @@ const OrderItemsStep: React.FC<WizardDataProps> = ({ data, onDataChange }) => {
 
 // Step 3: Delivery & Payment with ALL fields
 const DeliveryPaymentStep: React.FC<WizardDataProps> = ({ data, onDataChange }) => {
-  const hasGeneratedOrderNumRef = useRef(false);
-
   const [orderData, setOrderData] = useState({
     // Required fields
     requestedDeliveryDate: data.requestedDeliveryDate || '',
@@ -604,26 +602,6 @@ const DeliveryPaymentStep: React.FC<WizardDataProps> = ({ data, onDataChange })
     metadata: data.metadata || '',
   });
 
-  // Auto-generate order number if not provided
-  // Only watches orderNumber field to avoid unnecessary re-renders
-  useEffect(() => {
-    // Only auto-generate order number if:
-    // 1. We haven't generated before
-    // 2. Order number is empty
-    if (!hasGeneratedOrderNumRef.current && !orderData.orderNumber) {
-      hasGeneratedOrderNumRef.current = true;
-      const orderNum = `ORD-${Date.now().toString().slice(-8)}`;
-      const newData = { ...orderData, orderNumber: orderNum };
-      setOrderData(newData);
-      onDataChange({ ...data, ...newData });
-    }
-
-    // If user manually clears the order number, allow regeneration
-    if (hasGeneratedOrderNumRef.current && !orderData.orderNumber) {
-      hasGeneratedOrderNumRef.current = false;
-    }
-  }, [orderData.orderNumber]); // Only watch orderNumber - prevents unnecessary interference
-
   // Update parent whenever order data changes
   const handleOrderDataChange = (newOrderData: any) => {
     setOrderData(newOrderData);
@@ -660,17 +638,18 @@ const DeliveryPaymentStep: React.FC<WizardDataProps> = ({ data, onDataChange })
 
         <div>
           <label className="block text-sm font-medium text-[var(--text-secondary)] mb-2">
-            Order Number
-            <Tooltip content="Auto-generated order reference number">
+            Order Number (Read-only - Auto-generated)
+            <Tooltip content="Automatically generated by backend on order creation (format: ORD-YYYYMMDD-####)">
               <Info className="inline w-4 h-4 ml-1 text-[var(--text-tertiary)]" />
             </Tooltip>
           </label>
           <input
             type="text"
-            value={orderData.orderNumber}
-            onChange={(e) => handleOrderDataChange({ ...orderData, orderNumber: e.target.value })}
-            placeholder="ORD-12345678"
-            className="w-full px-3 py-2 border border-[var(--border-secondary)] rounded-lg focus:outline-none focus:ring-2 focus:ring-[var(--color-primary)] bg-[var(--bg-primary)] text-[var(--text-primary)]"
+            value={orderData.orderNumber || 'Auto-generated on save'}
+            readOnly
+            disabled
+            placeholder="Will be generated automatically"
+            className="w-full px-3 py-2 border border-[var(--border-secondary)] rounded-lg bg-[var(--bg-secondary)] text-[var(--text-tertiary)] cursor-not-allowed"
           />
         </div>
       </div>