Add JSON files for Payment Gateway Interface and API documentation updates

- Created a new JSON file for the PaymentGatewayInterface.php, detailing its methods and return types.
- Added a JSON file for payment.md, documenting various API endpoints and their parameters, responses, and errors.
- Introduced a JSON file for fix-admin-modal-and-calendar.md, outlining issues and solutions related to admin modal and calendar functionalities.

assets/admin/pages/ClinicDetailPage.tsx

@@ -781,7 +781,7 @@ export default function ClinicDetailPage() {
       </div>
 
       {/* ── Main grid ── */}
-      <div style={{ display: 'grid', gridTemplateColumns: '1fr 300px', gap: 'var(--gap)', alignItems: 'start' }}>
+      <div className="split-2">
 
         {/* Left column */}
         <div style={{ display: 'flex', flexDirection: 'column', gap: 'var(--gap)' }}>