feat: Add flags to Country select + Bank account repeater for BACS

1. Added Emoji Flags to Country/Region Select ✅

   Before: Indonesia
   After:  🇮🇩 Indonesia

   Implementation:
   - Uses same countryCodeToEmoji() helper
   - Flags for all countries in dropdown
   - Better visual identification

2. Implemented Bank Account Repeater Field ✅

   New field type: 'account'
   - Add/remove multiple bank accounts
   - Each account has 6 fields:
     * Account Name (required)
     * Account Number (required)
     * Bank Name (required)
     * Sort Code / Branch Code (optional)
     * IBAN (optional)
     * BIC / SWIFT (optional)

   UI Features:
   ✅ Compact card layout with muted background
   ✅ 2-column grid on desktop, 1-column on mobile
   ✅ Delete button per account (trash icon)
   ✅ Add button at bottom with plus icon
   ✅ Account numbering (Account 1, Account 2, etc.)
   ✅ Smaller inputs (h-9) for compact layout
   ✅ Clear labels with required indicators

   Perfect for:
   - Direct Bank Transfer (BACS)
   - Manual payment methods
   - Multiple bank account management

3. Updated GenericGatewayForm ✅

   Added support:
   - New 'account' field type
   - BankAccount interface
   - Repeater logic (add/remove/update)
   - Plus and Trash2 icons from lucide-react

   Data structure:
   interface BankAccount {
     account_name: string;
     account_number: string;
     bank_name: string;
     sort_code?: string;
     iban?: string;
     bic?: string;
   }

Benefits:
✅ Country select now has visual flags
✅ Bank accounts are easy to manage
✅ Compact, responsive UI
✅ Clear visual hierarchy
✅ Supports international formats (IBAN, BIC, Sort Code)

Files Modified:
- Store.tsx: Added flags to country select
- GenericGatewayForm.tsx: Bank account repeater
- SubmenuBar.tsx: Fullscreen prop (user change)

admin-spa/src/components/nav/SubmenuBar.tsx

@@ -2,17 +2,22 @@ import React from 'react';
 import { Link, useLocation } from 'react-router-dom';
 import type { SubItem } from '@/nav/tree';
 
-type Props = { items?: SubItem[] };
+type Props = { items?: SubItem[]; fullscreen?: boolean };
 
-export default function SubmenuBar({ items = [] }: Props) {
+export default function SubmenuBar({ items = [], fullscreen = false }: Props) {
   // Always call hooks first
   const { pathname } = useLocation();
   
   // Single source of truth: props.items. No fallbacks, no demos, no path-based defaults
   if (items.length === 0) return null;
 
+  // Calculate top position based on fullscreen state
+  // Fullscreen: top-16 (below 64px header)
+  // Normal: top-[88px] (below 40px WP admin bar + 48px menu bar)
+  const topClass = fullscreen ? 'top-0' : 'top-[calc(7rem+32px)]';
+
   return (
-    <div data-submenubar className="border-b border-border bg-background md:bg-background/95 md:backdrop-blur md:supports-[backdrop-filter]:bg-background/60 sticky top-0 z-20">
+    <div data-submenubar className={`border-b border-border bg-background md:bg-background/95 md:backdrop-blur md:supports-[backdrop-filter]:bg-background/60 sticky ${topClass} z-20`}>
       <div className="px-4 py-2">
         <div className="flex gap-2 overflow-x-auto no-scrollbar">
           {items.map((it) => {