docs: Update PROJECT_SOP and add customer data flow analysis

1. Updated PROJECT_SOP.md:
✅ Added mobile card linkable pattern with full example
✅ Added submenu mobile hiding rules and behavior matrix
✅ Documented stopPropagation pattern for checkboxes
✅ Added ChevronRight icon requirement
✅ Documented active:scale animation for tap feedback
✅ Added spacing rules (space-y-3 for cards)

2. Created CUSTOMER_DATA_FLOW_ANALYSIS.md:
✅ Comprehensive analysis of customer data flow
✅ Documented 2 customer types: Guest vs Site Member
✅ Identified validation issues in OrdersController
✅ Found weak ! empty() checks allowing bad data
✅ Documented inconsistent validation between controllers
✅ Created action items for fixes
✅ Added test cases for all scenarios

Key Findings:
❌ OrdersController uses ! empty() - allows 'Indonesia' string
❌ No phone number sanitization in order creation
❌ No validation that phone is actually a phone number
✅ CustomersController has better validation (isset + sanitize)

Next: Investigate source of 'Indonesia' value and implement fixes

admin-spa/src/routes/Coupons/CouponForm.tsx

@@ -80,8 +80,8 @@ export default function CouponForm({
 
   const tabs = [
     { id: 'general', label: __('General'), icon: <Settings className="w-4 h-4" /> },
-    { id: 'restrictions', label: __('Usage restrictions'), icon: <ShieldCheck className="w-4 h-4" /> },
-    { id: 'limits', label: __('Usage limits'), icon: <BarChart3 className="w-4 h-4" /> },
+    { id: 'restrictions', label: __('Restrictions'), icon: <ShieldCheck className="w-4 h-4" /> },
+    { id: 'limits', label: __('Limits'), icon: <BarChart3 className="w-4 h-4" /> },
   ];
 
   return (