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/merchant/[id]/login/page.tsx

@@ -0,0 +1,103 @@
+'use client';
+
+import React, { useState } from 'react';
+import { useRouter, useParams } from 'next/navigation';
+import { ShieldCheck, ArrowRight, Lock, Building2 } from 'lucide-react';
+
+export default function MerchantLoginPage() {
+    const [apiKey, setApiKey] = useState('');
+    const [isLoading, setIsLoading] = useState(false);
+    const [error, setError] = useState('');
+    const router = useRouter();
+    const params = useParams();
+    const id = params.id as string;
+
+    const handleSubmit = async (e: React.FormEvent) => {
+        e.preventDefault();
+        setIsLoading(true);
+        setError('');
+
+        try {
+            // We use an API route to verify the key and set a cookie
+            const response = await fetch(`/api/merchants/auth`, {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({ identifier: id, apiKey })
+            });
+
+            const data = await response.json();
+
+            if (response.ok) {
+                router.push(`/merchant/${id}`);
+                router.refresh();
+            } else {
+                setError(data.error || 'Geçersiz anahtar.');
+            }
+        } catch (err) {
+            setError('Bir hata oluştu. Lütfen tekrar deneyin.');
+        } finally {
+            setIsLoading(false);
+        }
+    };
+
+    return (
+        <div className="min-h-screen bg-[#F8FAFC] flex flex-col items-center justify-center p-6">
+            <div className="w-full max-w-md space-y-8 animate-in fade-in slide-in-from-bottom-4 duration-700">
+                <div className="text-center space-y-4">
+                    <div className="w-20 h-20 bg-blue-600 rounded-[32px] flex items-center justify-center text-white mx-auto shadow-2xl shadow-blue-100 mb-6">
+                        <Building2 size={32} />
+                    </div>
+                    <h1 className="text-3xl font-black text-gray-900 tracking-tight uppercase">Firma Girişi</h1>
+                    <p className="text-gray-400 font-bold uppercase tracking-widest text-[10px]">P2CGateway Güvenli Erişim Paneli</p>
+                </div>
+
+                <div className="bg-white p-10 rounded-[40px] border border-gray-100 shadow-xl shadow-gray-200/50 space-y-8">
+                    <div className="space-y-2">
+                        <p className="text-sm font-black text-gray-900 leading-tight">Yönetim anahtarınızı girin</p>
+                        <p className="text-[10px] text-gray-400 font-bold uppercase tracking-wider">Size özel tanımlanan API Secret Key ile giriş yapın.</p>
+                    </div>
+
+                    <form onSubmit={handleSubmit} className="space-y-6">
+                        <div className="space-y-3">
+                            <div className="relative">
+                                <Lock className="absolute left-5 top-1/2 -translate-y-1/2 text-gray-300" size={18} />
+                                <input
+                                    type="password"
+                                    required
+                                    value={apiKey}
+                                    onChange={(e) => setApiKey(e.target.value)}
+                                    placeholder="••••••••••••••••"
+                                    className="w-full pl-14 pr-6 py-4 bg-gray-50 border-2 border-transparent focus:border-blue-500 focus:bg-white rounded-[24px] outline-none transition-all font-mono font-bold text-gray-900"
+                                />
+                            </div>
+                            {error && <p className="text-[10px] text-red-500 font-black uppercase tracking-widest pl-2">{error}</p>}
+                        </div>
+
+                        <button
+                            type="submit"
+                            disabled={isLoading}
+                            className="w-full py-5 bg-gray-900 text-white rounded-2xl font-black text-xs uppercase tracking-[0.2em] hover:bg-black transition shadow-xl disabled:opacity-50 flex items-center justify-center gap-2"
+                        >
+                            {isLoading ? 'Doğrulanıyor...' : 'Paneli Aç'}
+                            {!isLoading && <ArrowRight size={16} />}
+                        </button>
+                    </form>
+                </div>
+
+                <div className="text-center pt-4">
+                    <button
+                        onClick={() => router.push('/')}
+                        className="text-[10px] font-black text-gray-400 uppercase tracking-widest hover:text-gray-900 transition"
+                    >
+                        Ana Sayfaya Dön
+                    </button>
+                </div>
+            </div>
+
+            <div className="mt-20 flex items-center gap-3 px-6 py-2 bg-blue-50 rounded-full border border-blue-100">
+                <ShieldCheck size={14} className="text-blue-600" />
+                <span className="text-[9px] font-black text-blue-600 uppercase tracking-widest">SSL 256-bit Uçtan Uca Şifreleme</span>
+            </div>
+        </div>
+    );
+}