feat: implement merchant dashboard, secure auth, and short_id system

- Added dedicated merchant dashboard with analytics and transactions
- Implemented API Key based authentication for merchants
- Introduced 8-character Short IDs for merchants to use in URLs
- Refactored checkout and payment intent APIs to support multi-gateway
- Enhanced Landing Page with Merchant Portal access and marketing copy
- Fixed Next.js 15 async params build issues
- Updated internal branding to P2CGateway
- Added AyrisTech credits to footer

app/api/mock-complete-payment/route.ts

@@ -1,5 +1,5 @@
 import { NextRequest, NextResponse } from 'next/server';
-import { supabaseAdmin } from '@/lib/supabase';
+import { supabaseAdmin } from '@/lib/supabase-admin';
 
 export async function POST(req: NextRequest) {
     try {