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/layout.tsx

@@ -13,8 +13,8 @@ const geistMono = Geist_Mono({
 });
 
 export const metadata: Metadata = {
-  title: "Create Next App",
-  description: "Generated by create next app",
+  title: "P2CGateway | Güvenli Ödeme Altyapısı",
+  description: "P2CGateway ile farklı ödeme sistemlerini tek elden yönetin. Stripe, Cryptomus ve daha fazlası.",
 };
 
 export default function RootLayout({