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

components/admin/QueryRangeSelector.tsx

@@ -0,0 +1,29 @@
+'use client';
+
+import React from 'react';
+import { useRouter, useSearchParams } from 'next/navigation';
+
+export default function QueryRangeSelector() {
+    const router = useRouter();
+    const searchParams = useSearchParams();
+    const currentRange = searchParams.get('range') || '30';
+
+    const handleRangeChange = (e: React.ChangeEvent<HTMLSelectElement>) => {
+        const newRange = e.target.value;
+        const params = new URLSearchParams(searchParams.toString());
+        params.set('range', newRange);
+        router.push(`/admin?${params.toString()}`);
+    };
+
+    return (
+        <select
+            value={currentRange}
+            onChange={handleRangeChange}
+            className="bg-gray-50 border-none rounded-xl text-[10px] font-black uppercase tracking-widest px-4 py-2 outline-none cursor-pointer hover:bg-gray-100 transition-colors"
+        >
+            <option value="30">Son 30 Gün</option>
+            <option value="7">Son 7 Gün</option>
+            <option value="14">Son 14 Gün</option>
+        </select>
+    );
+}